I really like mummy and toddler groups. I agree some can be very cliquey but its important to try many and find one you feel most comfortable with.
Luckily, I live in a area with lots of children's centres so there are plenty of sessions free and within walking distance. I tried lots as I was looking for friends too, and I found that I just didn't click with a lot of then women there, it was all a bit plastic. There was one group in particular that I perserveered with because the lady that ran it was so lovley, I was going for a few months and there would be some mums that were regulars and some others pop in, we'd all have a really good chat and then they'd never come back. I kept going in the hope i'd see some of them again
It then started to be regular mums. After posting something similar on MN I wanted to try so I kept telling myself that I'd just say 'we should all have coffee afterwards one day!?' in a very casual, I dont really care what the answer is' way but deep down I was desperate for them to say yes but I kept chickening out.
One of the mums I got really friendly with, told me she was heading back to work in a couple of weeks so they wouldn't be attending anymore classes, I took this as my opportunity. I said we should all go for cake or something next week, and to my surprise 4 of the mums looked over the moon and said they were waiting for someone to ask they were a bit shy!
We went and it was a bit awkward at first without being distracted by toys and babies, but over time it became more comfortable and not only about the babies! We meet once a week when we can and so its nice to have company going to the park or for a walk.
So I say give it time, you don't just make friends straight away, it has to build up as said up thread. Find one you like and overtime you'll get to know the mums that are there and take it from there.
Good luck.