I used to live in Souhtern Ca. and work in that area. The Hilton, if my memory and coffee are working, is not far from the airport. I wouldn't plan on too many walking trips around the area at night and there's not much to see during the day. That area is very 'downtown' and the people tend to talk to themselves.
Your best bet would be to rent a car & grab a map. Take the 105 West (it's almost attached to the back of the airport), it will end & you'll be on a 4 lane street. Keep going until you hit water. Very nice beaches in that area & it's a 15 minute drive (?).
If you like shopping . . . umm . . . The Ontario Mills Mall is about an hour away & it's hugh. The Cerritos Mall is small.
If you pass by a Green Burrito (not the Carls Jr partner but the real McCoy) you really need to try it! Best burritos in southern Ca. It's going to be a small hole in the wall but great food.
If you don't have time for that . . . try to book your hotel for somewhere closer to the port in a neighboring city like Cerritos. Long Beach, where the port is is nothing but trucks and more strange people on the streets.
feel free to email me with any questions. I was in that area for the better part of 25 years. That's why I moved to another state. <BG> There are some nice areas though!