M.S.
I'm shocked at those who think its so difficult to make friends in Pittsburgh, since I've never had that problem and I only know one person (who's also a very closed/private person) who's not raved about the ease of making friends. Maybe its the South Hills location (??)(I'm out by the airport), but that's a shame and makes me sad.
Anyway - I'm part of a group on Meetup (its for moms who had babies later in life 35yo+). We have a ton of get togethers as a group or on our own (two of us met the other day for lunch). Some of those moms belong to other Meetup groups (based on religion, lifestyle, location, etc). My experience with Meetup has been the same as my experience with Pittsburgh in general - folks love meeting folks and welcome newcomers with open arms.
I've been part of two MOPS groups and have mixed experiences/reviews - one of them had some in-fighting with the 'board members' and how the money was handled, causing gossip and bad feelings; the other seemed to take advantage of the moms who volunteered, they never got a break and ended up dropping out.
We also have friends met randomly at parks - we were at a park last week, there was a Meetup group that was there as well - while at the playground, we started talking and having fun with the kids and now we have new friends. We have friends from being part of a tour of downtown. We have friends from being in the peed's waiting room, while our sons acted like they were long lost brothers. We have friends from playing at the fountains at SouthSide Works, while my son and her son swapped dump trucks.
Good friends are a MUST, so I wish you (and others) all the luck!!!!!