I also just got my plates in the mail yesterday, for my Model 3. Purchased & took delivery of my car on 3/31, and the DMV registration shows the registration paperwork was printed out on 4/20. Plates were received in the mail on 5/13.
Good thing too because SCE sent me a reminder email to hurry up and submit a copy of my official DMV registration in order to get my $1000 rebate, or they would cancel my application at the end of this month. Didn't need it through for the CVRP rebate.
I didn't apply for the HOV decals yet (will wait to 2021 since I'm not driving much these days, and will be working from home a lot this year), but in the past when I've always applied for them - 6 total sets over the past 5 years, usually once the DMV cashes your check then the process is fast and the stickers show up in the mail about a week later. It's usually the waiting, from the time you mail in your app until you see your check has been cashed, that is a long time.