I was going to recommend forgetting about UA and just taking Lan LAX-LIM - that's what I ended up doing, and was happy about it.

This trip report has some details about my experiences going to Peru; posts 1 and 12 talk about Lan. I liked the service in Y, and even more in C. It's worth the extra $150 for C from MEX-LIM.

This hardly needs to be repeated, but I'll do it anyway: even before Varig left, *A was weak sauce in South America. Now it's not even an option except for simple round-trips to a select few cities.