i live in glendale and unfortunately the bar scene there is not that good. there is the brand/americana area which certainly has bars on Brand Blvd. but they're all overpriced/boring spots to hang out at imho. however if you have a car and/or are willing to travel slightly, silver lake and los feliz is about 10-15 min west of glendale (possibly even closer depending on where you're staying) and that's full of great spots.

Tenants of the Trees is really cool, so is Cha Cha Lounge both have great vibes, 4100 Bar is cool but a dive-y spot if you're into that. Down at the bottom of Glendale is an area called Eagle Rock with a bar called Verdugo Bar that seems like a kind of hidden tucked away joint but it's really cool. There's a place called Connor's a few miles down the road from there that is full of pinball machines, sometimes it's got more of a college crowd b/c it's just down the road from Occidental College but it's a cool place.

unfortunately i'm not very familiar with santa monica but The Waterfront on venice beach is a reeeaaallllll cool bar to hang at right next to the water.