L.L.
I think the best recommendations come from other moms. That's how I found all the preschools I looked at before choosing one. I see that you live in Beltsville...I'm from Olney, and when I was looking for a preschool in 2006, all the good ones seemed to fill up really quickly. I don't know if you'll run into the same problem, but I'd get out there and start looking soon! My son went to Millcreek Preschool in Derwood and we both totally loved it!! His teacher was fantastic and everyone there was really great. The other ones I looked at that I heard were equally fantastic were Creative Learning Center in Olney and The Ark at Oakdale Emory church in Olney. That might be too far for you to travel?? A great resource is your local MOMs club. You can check out their website and see if you have a group near you. I really loved being a part of my group and I was sad I had to leave it when I moved.
http://www.momsclub.org/links.html
Whatever you choose, I would do in class visits or at least take a tour of each school before you decide on one...seeing the teachers in action will give you a good feel of things. And trust your instinct!! If a school doesn't feel right, move on to the next.
Good luck!!