That is a good question that I'd be interested to know if someone else has any insight. I just signed my 14 month up for a 2 day a week (9-2) Mother's Day Out program at a nearby church. I went and visited to check it out and it was great. You could look into something like that too. As for the play groups, I am guessing you could ask to visit before actually joining to make sure you and your daughter get along with the kids/moms. You could probably visit a few just to be sure. Chemistry is a big thing.
As far as playgroups go, I think it is really going to depend on what you are looking to get out of it. There is a local organization where I live that iffers a playgroup that included newborns to three year olds once a week. my son and I went went he was about 6 months old. they read storys sang and did fingerplays then had toy play time. I did not care for it because the age group was too big and the moms were more interested in talking to eachother rather than tending to their children so that did not work for us. I got onto this website and went to the parents tab and typed in my zip code I found a large group of women in my zip code with children around my sons age. now we plan play dates to the park,zoo etc. this has worked out best for us because the children are around the same age and we can let the kids play while we socialize. Good luck!