None of them except maybe Continental, since none of them are in the terminall your flight will be leaving from, and thus you won't have access to them. To get past security, you have to have a boarding pass for the gates past security in that terminal. US Airways is in terminal 1, Northwest in terminal 2, Alaska in terminal 3, etc, and United is in joined terminals 7&8 (and even part of 6). Continental is also in 6, but I'm not sure how it works between United and Continental inside terminal 6 (all I know about United in terminal 6 is that that's where United's premium check-in is, but that's landside, and the lounges are all airside.

Meanwhile, the free WiFi is in United's lounge (through a card they give you when you're admitted to the lounge), not throughout LAX in general. (I'm not familiar with all the other lounge's WiFi policies, but it varies from lounge to lounge as to who gets access to free WiFi. For example, at AA's lounges, people who get are AA lounge members get free WiFi but people who get in on OneWorld or AAdvantage status don't get free Wifi. Thus you may need to explain on what qualificaion you'd get into each of these lounges.)