Although relatively speaking Brazil doesn’t attract that many foreign visitors a year, the image it manages to project to the outside world is overwhelmingly positive: samba, impressive nature, happy-go-lucky, vibrant, sexy, full of optimism, with a nothing-can-bring-me-down attitude. In a word: Rio.

For the lucky few, this is perhaps a reality. Even for some outside Rio. Money helps – as long as you’re locked away snug in your closed condominium. Even the masses get a break in February to dance and forget their problems (read: get drunk) in the dizzying Carnaval holiday.

For the foreign visitor, staying just a couple of weeks, this is the impression you’re likely to leave with. And if that person were someone like me, who is besotted with nature – this place is unrivalled. It’s a paradise. When I’m in the forest surrounded by toucans and parrots, I don’t want to be anywhere else.

But then the road inevitably turns back to the cities and their dark goings-on. My heart sinks every time.

I’m not a city boy – although I lived in London for five years and grew up just a few miles from the quaint city of Canterbury in England’s southeasternmost corner. I’m much more at home around forests, fields and coastlines.

And I’m sure it’d be true of the vast majority of cities in Brazil, Latin America and further afield, but for me that place is my city in southern Brazil – Curitiba, with its “modern, European” ways (words we’re all continually force-fed here – whoever thought these words up has never been anywhere modern or European). All that is wrong with the world comes into sharp focus as it brazenly wanders down the street in the light of day.

Forget the discourteous people that blight any city, and particularly Curitiba. Forget the over-tattooed, disgusting massive-hole-in-the-earlobe crowd which seemingly represents half the population here. Forget things like bent politicians and not recycling enough. Forget graffiti, traffic and the taste of the air pollution in the back of your throat as the environmentally-friendly buses chug thick, black smoke into the already-polluted air.

I mean, the real wrongs of this world – homelessness, prostitution, destructive vandalism, violence, muggings, drug-taking – it’s all far too easy to see here. Knife and gun crime is rife in many places – and although I haven’t yet come face-to-face with it here, I have friends here who have and have been lucky on most occasions only to come into contact with the former.

Just walk around the area near Rua Treze de Maio – 13 May Street – a date, by the way, that is meant to set off visions of the end of slavery in the minds of Brazilians.

On one side – prostitutes, not just at dusk but all day long. Some of them are painfully young, their pimps striding around them. All the phone booths here are laced with calling cards. There seems to be no shame in it. In fact, all you see on the pavements right now are bits of paper promoting hookers (and politicians).

On the other side – a teenager smoking crack out of a can. I’ve seen this a number of times and I feel I am getting desensitised to the sight. Look too long at someone and they think you’re looking to score drugs.

The rate of homelessness is Curitiba is also sky-high. People come in from the rest of the state – some say they are bussed in by other cities – and just hang around the parks and squares. The sight of someone putting their hand in a bin and pulling out a half-smoked cigarette or a tin can they can sell off, as it was unusual, used to repulse me in London. I see it every 10 minutes here.

On the corner of Treze de Maio stands a mugger, biding his time until the next victim walks into his web. Today it was my other half – the thief waited until the road was quiet and then threatened him, apparently harbouring a gun under his jacket. Luckily, he escaped unharmed and none the worse for the ordeal.

Depending on the survey, Curitiba ranks between first and sixth most violent city in Brazil. And although this is centred largely in one very dodgy area in the suburbs, the city is not a place to walk around after 10pm or so.

I am aware that these things can be found in most cities, but they are so on show, so easily seen here, that I forget how horrific they are.

And so what? Big cities in Brazil are like that: deal with it or go elsewhere. Okay, but these cities are going to be broadcast to the world from next year – with the FIFA Confederations Cup beginning, and then to massive audiences in 2014 (World Cup) and 2016 (Olympics).

Despite my complaints about Curitiba and Brazil’s shortcomings – “I complain therefore I am” would go well on my gravestone, my other half would say – I care. Obviously, I care. That’s why I complain. I have strong opinions about this place – and although I could easily up-sticks and skedaddle, I just wish people would take the opportunity, the billions of reais of opportunity, and do something with it that would benefit people.

Why do I care? Because although I have met a lot of lazy, lying, underhand people here – most of them have been landlords – I have met many more nice people and it saddens me that they have to put up with it, particularly when politicians are syphoning off the money that could be sorting it out.

I’m being too simplistic, I know. But it’s so frustrating when you see that Brazil has the potential to be an AMAZING country, if only it were to take the bull by the horns and sort itself out, without wasting money on looking fancy, trying to keep up with the Gonzálezes and the Wongs with predictable wastes of money like bullet trains and 4G networks.

Sometimes I feel like a parent berating a child. It’s so obvious to me that what you’re doing is wrong. But then perhaps I’m wrong, and there’s a better way… with improvements having started deep inside the system that will soon come to the surface. Parents don’t always know best. Butt out, gringo.

But I fear that, with nosey journalists and visitors soon coming to Brazil in much bigger numbers, more harm will be done to the country’s image than good, and that would not be good for the country as a whole – in terms of investments and tourism.

And where London 2012 brought a sense of pride back to the British people, I can just foresee a situation where a slew of behind-the-scenes stories will emanate from Rio 2016, shaming Brazilians and doing nothing for their optimism – which I see as the one thing that gets them through these sometimes shocking conditions – not to mention the country’s more abstract new-found sense of place on the world stage.