if you haven't already registered and you want to take it at the end of january, you'd better call to make sure space is still available then (or try to register online at http://www.mba.com
). end of the month test dates can be hard to come by and can fill up fairly far in advance. if you know that's when you want to take it, register as soon as possible. although i don't know if scheduling is as tight in serbia as it is in big cities in the US!
many US schools have multiple application deadlines, with May 1 being one of the MUCH later ones. Most have deadlines that are already starting. Take a look at the deadlines for the schools you're interested in - May 1 will be too late for most. They're already mailing acceptance letters by then. If you want to be considered for scholarships or other financial aid, you'll probably need to apply in February.
It takes 2-3 weeks for your scores to reach the schools, so if you take it at the end of January and the round you're applying in has a deadline from late February or later, you'll be ok.
Do some more research to make sure you prepare in time.