On a positive note - Montessori has tons on offer when done well. My son knew all of the continents by the end of the first semester of his second year and had pin punched every single continent out of paper and assembled a "globe" picture. You won't find that kind of activity I don't think at most Pre-K's. All the work he did from age 2 3/4 or so was geared towards toddler's and their need to feel and touch things which was great.
I would ask lots of questions about the administrative side of the school and ask other parents how they find the communication at the school. This was a huge let down at our school - though I hear its now more organized. As you can't possibly know what your kids are doing all day once you let them go, what the teacher's tell you and how soon they tell you is important. How attentive they are is important. One time my child went into school and another child started yelling at him, and he was yelling back and it was obvious that what he had been telling me about not liking this child was true and had gone on rather a long time. Other parents that didn't work filled me in on a lot of other incidents I would never have known about. It also took the school ages (one whole semester) to tell me that he was starting to have some behavioral issues when he was a young 4 - and I felt like they had waited way too long.
Also ask about how they structure their playground time. I found our school wasn't always really monitoring the playground the same way they monitored the work indoors - and outside time was often when the worse incidents occurred or when the worst influence from certain problem children they took in one year occurred. I felt that adversely affected my son and exposed him to things I personally had been keeping away from him.
