There is a direct bus connection to Westwood, and UCLA. You may either check the web site of the Linguistics Department for information and useful maps, or use the trip planner to find out. Basically, your best connection is the Green Line (or Culver City) Bus Number 6, going along Sepulveda Boulevard all the way to UCLA Ackerman (it is not worth changing buses to get to Hilgard, just walk). The only complication in this is that the buses do not stop at the terminal itself. Rather, they stop at Lot C, which is a car park. There are free buses at Los Angeles Airport that take you from the terminal to Lot C, where you can then get on the bus.
Starting mid June there is an Express Connection between UCLA and Westwood, stopping only at LAX (each terminal!) and UCLA. The fare is USD 4 one way. More than a standard bus but still far cheaper than a taxi. The link shows you a map. Opposite the bus stop is UCLA parking lot 36. There is a bus stop in front of that parking lot. That is where the UCLA bus shuttle stops. It is a free service offered by UCLA. It takes you to Murphy Hall (the actual bus stop is in front of the faculty center), and from there you can walk to IPAM within 5 minutes.