while the blocos in the zona sul are normally smaller and closer to the accommodations of most international visitors, appropriate rest is mandatory before partaking into any of the larger blocks in the center of rio.

in fact, getting back to apartments and hotels from the center of rio can be difficult during carnaval. 

as the huge crowds stop traffic, there could be a shortage of taxis, and typically public transportation will be spotty and overcrowded - best is always setting a meeting point and pre-arranging a taxi ride back to the zona sul in advance. 

in general common sense and caution are always the best advice, and blocos are no exception.