I've been wanting to do the same thing and according to this book that I'm reading about avoiding common pilot errors (Written from a controller's perspective) it is absolutely encouraged for all pilots to take a tour of the ATC facilities and get a fell for how it works. The book says to give the facility a call, let them know who you are, who might be coming with you, what exactly you would like to see, when you would like to come by etc. and they should be happy to set something up for you.