I was in Colombia last year during Carnaval and we went to Cartagena and Rodadero for awhile to beat the crowds a bit since I had already been to Carnaval two other times, but then we decided to go back to BAQ to catch a couple days of Carnaval action. And I made some calls and had reservations for a room somewhere that cost like $200 when it usually only cost $40, then when I got there they raised the price. And it was a dump. So I ended up wasting half a day looking for another place and it cost like $300!!! So lesson learned.
Anyone going to Carnaval should try to catch the "Guacherna" which is a separate street parade which for me, was much more wild, fun, etc. It is more of the people themselves in the streets, more drums, more action.
The Carnaval itself, if you are sitting in the stands, seemed a bit boring to me. Just the same kind of parades over and over again.
The real fun was when you are in the streets participating. Just watch your cash. Lots of pickpockets.
One time I was there, a guy got a bunch of flower thrown in his face by a group of teenagers (which is completely normal), but while he as temporarily "blinded" they picked his pockets clean.