There are bike paths all along the river and there's lots of team rides on the weekends. There are plenty with extremely flashy road bikes, cycling is becoming more and more popular, a lot of the teams meet at the Carrefour on Libertador. However if you bring a nice road bike, also buy a cheap one that you don't mind leaving on the street when you go into the supermarket etc. I have two, the one I take to the supermarket / on errands I think the childseat on the back is probably worth more than the bike itself. In fact if it ever got stolen I'd mourn the loss of the seat but not the bike (my child is too big for the seat now but I end up using it for groceries etc!)