I managed to get $450 ish round trip from Calgary to LAX, so I would guess you can get them a bit cheaper. PSP and Ontario are way better options than LAX, but they will cost more those weekends due to demand. Calgary to PSP was $1200+ for the same days as my flight to LAX.
If you fly Allegiant air from Bellingham, it's like $88 one way to Palm Springs. That's on the Wednesday though. My friend did that this year and then we all crashed at a hotel real cheap for the one night. If you can come down that one day early, everything is cheaper since the demand doesn't really start til the next day.