Hotel near San Salvador airport
There is a Quality Inn about one mile from the airport. It is new and secure. Down side is that it is really in the middle of nowhere and will make for a very boring stay. $90 per night.
If I were you, I would pay $25 and take a taxi to La Libertad, a coastal fishing town about half an hour up the coast from the airport. There is a nice new hotel there, Pacific Sunrise, that have rooms starting at $40, larger suites for $65 per night. The less expensive rooms have views of the gas station and zona de tolerancia.
There are scores of seafood restaurants within walking distance. You can also walk to the fishing pier and see some great sights.
Hope this helps.