I would Google search for Irish Pubs in the San Fernando Valley and then call the ones that are closest to you and work out from there and see what you find. I know that McG's in Chatsworth is one such establishment.
McG's Irish Pub & Grill
21356 Devonshire St, Los Angeles, CA 91311
I hate to say it but you'll have to come over the hill to Santa Monica. Sonny Mclean's is your best bet to find a Boston friendly crowd in So Cal. I have many friends who make the trek from the Valley on Sox, Celts, B's, and Pats game days. It gets very crowded very quickly especially on Patriots game days. And just looking at their menu online they now are touting a Chef and maybe that means significant improvement to what once were mediocre clam rolls and awful lobster rolls.
Sonny McLean's Irish Pub
2615 Wilshire Blvd, Santa Monica, CA 90403
> Have you tried finding a bar full of Laker fans in Boston?
As unlikely as it might seem, there _is_ a Boston-friendly place, but not in SFV: Sonny McLeans in Santa Monica. More info in this thread:
I agree you wouldn't find a Laker-friendly bar in Boston. I grew up in Boston, and one reason I live in LA rather than Boston is that LA embraces diversity in a way Boston doesn't.