You can contact a broker before or after you sign up for a school but I think most people do it after they get their license officially. Be sure to contact multiple companies so you can see where you would fit in well and see where you think would provide the best training.
I think all the real estate schools are pretty similar in my opinion, most people suggest Allied but there are some other similar ones like RealEstateExpress.com. Just make sure whichever school you choose is DRE approved. You can call the DRE and ask if you aren't sure.
Also, you are better off talking to as many people as possible and to as many companies as possible... the more information you have the better you can make an informed decision.
Talk to franchise brokers, like c-21, prudential or keller williams, but don't forget to tak to smaller shops as they offer quite a different experience.. that way you can compare.
I just called to ask her a couple of questions the other day and even though I'm no longer a student she still took time out of her busy day to give me sound advice and leadership. Now that's what a real school of instruction is all about.
Kenneth B Dorfman Real Estate
DRE # 675912