I've only been playing this game for a couple weeks and have pretty much completed the game. After searching many sites on this game, I've noticed that 3 locations seem to be left out of walkthroughs and cheats (aside from the unlocka ll locations cheat) So here's afew hints to help you unlock all locations without cheating and get a few bonuses too. A huge hint: for every location you are at, (aside from the first) there are other sims that you can control that may need help. Check each sim that you can control. If they have a gold or platinum want then this sim is in need of your aid. Help fulfill all of their gold and platinum wants until all 4 of there wants are green. This should then unlock a location or give you and added bonus. Out of the several times I've played and completed the game, these following locations have been tied to these sims. It may change from gameplay to gameplay but if you follow my above hint, you'll be able to open all locations. I have yet to help the final 3 sims. I kinda lose interest once I've seen all of the locations but I'm working now to see what these final three sims uncover. Here's the locations tied to their helped sims:
Shoreline Trails: Pretty simple, everyone gets here. Just fulfill your sims gold wants (usually unlocked after you buy the bed)
Cliffside Retreat: Fulfill all of your sims needs until they want to defeat Torin at foosball at the Shoreline Trails location. Beating him will unlock this location.
HMS Amore: Fulfill Isabella's gold and platinum wants at Cliffside Retreat.
Mesa Gallery: Fulfill Hector's G&P wants from the HMS Amore location.
Sunset Canyon: Fulfill Betty's G&P wants from the HMS Amore.
Andromeda Arms: Fulfill XHT-F's G&P wants from the Alien Crash Site location.
Jugen House: Fulfill Larry's G&P wants from the Tranquility Falls location.
Tranquility Falls: Fulfill Red S's G&P wants from Sunset Canyon.
Alien Crash Site: Fulfill Chantel's G&P wants from Tranquility Falls.
Bio Dome: Fulfill XY-XY's G&P wants from Alien Crash Site
Orbit Room: Fulfill Billy Spector's G&P wants from Sunset Canyon.
Opening credit bloopers: Fulfill Noel's G&P wants from Bio Dome.
With all of these, you should try to fulfill your sims G&P wants first until they ask you to help a sim or all of their wants turn green too. After your sim is satisfied, go after helping the sims listed above. It's best if you clear a location of all sims with gold and platinum wants (making them all green) before moving on to your next location to make sure all of your bases are covered. Sometimes you'll uncover more than one location without relocating to a new lot. :) Hope this helps. I'll update when I figure out what the final 3 sims uncover. I know they won't be lcoations.