Hi, if you're interested to ride your bike in Brazil there are lots of very nice trails pretty much everywhere in the country.

There are some nice mountain bike marathon races as well, such as:

Iron Biker - www.ironbiker.com
Big Biker - www.bigbiker.com
Nissan XTerra Brazil - http://www.xterrabrasil.com - triathlon with mountain bike

You can also find more mountain bike races at:
http://www.ativo.com/Default.aspx

If you are interested to ride your mountain bike in Brazil let me know and I will certainly help you with some advices.

Cheers!