looking for low ping, and a big community with raiding small to medium sized raiding guilds to choose from. One that is alliance heavy
You can sort realms by time zone and population on the realm status page, if that helps! I can’t link it, but you should be able to find it by Googling WoW realm status.
You can see a list of which servers are in each data center here:
You can then use something like wowprogress.com or raider.io to see general population trends. Then I’d just poke around on the forums for the promising looking servers.
Alliance tends to have fewer big realms in general. From a quick look, Proudmoore is the biggest LA based server alliance-side, so you may want to start there.