Things are definitely more spread out in LA (and SoCal generally) than DC, the sights are spread all over the massive city and it can easily be an hours drive from one to the other just in LA itself. Public transport between places is sometimes good, mostly just OK and sometimes non existent. Parking in LA is simple enough but if you want to do a tour the HoHo buses are fine and have 3 routes. If you park at the Ovation Hollywood Mall on the corner of Hollywood Bvde and Highland Ave that’s convenient and inexpensive for the tours which leave from outside the Mall. There is also a Metro Station there so it’s one of the better linked areas in LA for Public Transport. Hollywood itself isn’t really something that takes too long to see unless you’re into wax museums, Ripleys museums and the like. JKL films across the road from the mall.
More worthwhile than Hollywood though is Griffith Park which has dozens of things to see and do, it’s not just the Onservatory. There are walks, trains, theatres, Museums, plenty to fill a day if so inclined. You could get a bus from the Ovation and the Dash service up the Hill into Griffith Park if you didn’t want to drive. There’s also the Beverly Grove area which has plenty to see with 2 good shopping malls, plenty of dining options, the Original Farmers Market, La Brea Tarpits, the Academy Museum of Motion Pictures, LA Museum of Contemporary Art (undergoing renovations but a small section is still open), the Petersen Automotive Museum all in a very nice neighbourhood. Couple of days worth of activities there.
Then of course there’s Santa Monica with its beach, promenade, the Pier and plenty of great dining. Grand Central Market, The Broad and Disney Concert Hall downtown. The Getty Center and Villa, drive up the coast a little to and through Malibu. Manhattan Beach, a small upscale beach town near LAX, Long Beach for the Queen Mary and Aquarium, the studio Tours (WB, Sony, Paramount) in Burbank, the museums at Exposition Park although they’re moving the space Shuttle at the CA Science Center at the end of the year and heaps more. LA can fill several week long trips, I always find something new.
For Beach Towns, my favourites are in Orange County (where Disneyland is) like Newport Beach, Laguna Beach/Dana Point and Huntington Beach. Any of those could fill a day except probably HB.
if you have 3-4 days you should consider moving hotels but if you want to do day trips you’ll need to use the car. There are plenty of day trip options but PT from Anaheim will take ages, like 2, 2.5 Hours into LA Union Station then another 30 mins to Hollywood, longer to go elsewhere. Anaheim to Santa Monica shows around 3hrs by PT vs about an hour driving.
Haven’t even talked about SD but that city also has a lot to offer. We have certainly done day trips to LA and SD from LA but much prefer moving hotels and staying closer to what we want to see. Always enjoy Newport Beach as a day or half day trip along with Laguna and Huntington Beaches.
As above, I’d consider flying into SD, spend your spare days there then drive to Anaheim and maybe do a day trip into LA. Or vice versa, fly into LAX (or Burbank or Long Beach which are easier to navigate than LAX), spend a few days, move to Anaheim for DL and do a day trip to SD.
Or fly into LA for 2-3n, get a car and explore, drive to Anaheim for 3-4n near Disneyland, drive to SD for 2-3n and fly home from SAN.