B.N.
Congratulations on motherhood!! I have one boy who is 3, they grow so quick, enjoy!! I have found playgroups through the following ways. Most cities offer little classes (parent and me) through Parks and Rec. My son was in one from 6 months until he was 2 1/2. There were 5 friends that went all the way through with him. They will be friends for a long time. Online you can look up Mom's Club which matches you with a club in your zip code which allows you to make friends with mom's near by. Online I also found Cool Mommies of Corona/Norco. They have a ton of things to do and cater to a variety of ages. If you are needing "mom time" I found MOPS is great. They can also be found online and give mom's that couple hours of free time with other mommies that may be going through some of the same things you may be.
I hope this helps, Congrats again : )