If you're just now asking about Oktoberfest, you're almost too late to the party. In Germany, Oktoberfest starts every year on September17 and runs through the first Sunday in October or October 3rd, whichever is later. (This year, that would be October 3rd.) But here, you have plenty of time to attend one or more Oktoberfest events.
I attended the opening Oktoberfest event at Coachella Valley Beer on September 17th. I'm not sure why they dubbed it an Oktoberfest event given they didn't have any German beer or any oom-pah-pahing but it was a lot of fun and it served the purpose of getting people in the door. Tomorrow, however, they will have a Laughtoberfest event from 2-10pm. It's not Oktoberfest-themed but there's no cover and it's lots of fun. They will have a Berliner Weisse on tap which is, generally, a tart wheat beer. Named 99 Problems, it's a collaboration with TKB. I haven't tried it but at least they're getting in the spirit of things.
I went to their Comedy Festival last year where Michael Longfellow was the headliner. Now, he's one of the newest cast members on Saturday Night Live. (You can see him on YouTube's Netflix Is A Joke: The Festival.) Who knows whom you might see this year?
I can't believe how many people don't know of Desert Beer. They're good people making really good beer. They're also opening a second location in Indio so that's something to keep an eye out for. (I certainly will be.)
La Quinta Brewing's Oktoberfest isn't until October 29 (at their Palm Desert location). They promise to have German beers, food, and authentic Bavarian music. They are even offering a prize for the best Oktoberfest-themed outfit - a $25 gift card to La Quinta Brewing. Might be worth breaking out the lederhosen.
Oktoberfest started early at Big Bear Lake on September 10th but runs every weekend through November 5th so you still have plenty of time. This is also a fun event but you must purchase a ticket to attend. Prices vary on when you go and where you want to be seated. It's also a bit of a drive from anywhere so if you don't have a designated driver, I strongly encourage spending the night at a local hotel or vacation rental.
In all cases, drink responsibly. Have a designated driver or take Uber and have yourself some Oktoberfest fun.