S.P.
My 4 year old attends Montessori and i will be sending my 2 year old there starting in July.
I LOVE Montessori. It has been a loving, fun and wonderful experience. I really can not say enough good things about Montessori. There is a loose structure to the children's day, allowing thing to go at their own pace.
I would suggest a tour as well. I went on 2 tours. I was wowed both times. Ask lots of questions, because it is really interesting to learn how everything works.... and it works really well.
One thing you might want to look into is is he Montessori school you are looking at is accredited. We go to the Montessori School in Manhattan Beach, which is accredited. I only mention this because Montessori schools that are accredited feel this is a big difference that is important. I do not think a non accredited school is bad, but it may not do things 100% Montessori.
Best of luck!