LA Galaxy has put out what must be a couple dozen billboards throughout the City for the last 5 years or so. I've seen them in many places. That's about it. Definitely see more LAFC bumper stickers on cars, and downtown, you see occasional people wearing LAFC clothing. I don't recall ever seen LA Galaxy gear on anyone outside the stadium. Both MLS teams get full pro sports listings and regular (though smaller) coverage in the LA Times along with the NFL, NHL, NBA and MLB, and usually results are reported on the radio (though often derisively).
Crew definitely get more attention since the Save The Crew movement succeeded. There were several electronic billboards around town welcoming Lucas Zelarayan when we acquired him a few weeks ago. It's not unusual to see people wearing Crew gear though less than Blue Jackets and neither is close to OSU.