The hotels across the street from the park on Harbor are fairly good. I've stayed at the Tropicana a couple of times and it wasn't the best, but not bad. A colleague stayed at the Fairfield Inn and quite liked it. My daughter and her husband just stayed at Del Sol and didn't have any complaints.
I've stayed at the Embassy Suites about two or three (VERY LONG) blocks down Harbor. ART has a stop there. I like the Embassy Suites because the rooms have two truly separate rooms (living room and separate closed off bedroom), a mini-kitchen (frig and microwave), and a real breakfast in the morning. Not having to hunt around for breakfast is a huge time savings.
Some hotels claim to have "suites" but they just have a partial wall dividing a sitting area from the bed(s). What I like about Embassy Suites is that you can put the kids to bed on the fold out couch in the living room, shut the door between the two rooms, and stay up a little longer.
I haven't had any real trouble with ART. Right at closing there might be a line. Others may have different experiences.