what is the average life span of lesbians and male homosexuals in the
USA?  how does it compare to the straight population?

In the past, attempts to come up with statistics of this type have
been the subject of some criticism:

http://psychology.ucdavis.edu/rainbow/html/facts_cameron_obit.html

I honestly don't see why It would be much less than anyone else.

I suppose that HIV might adversely affect the gay community.

Gay men tend to exercise more, since straights stop after marriage. 
Also, the nagging wife and screaming kids cause the breeder much
stress.

With regard to "Also, the nagging wife and screaming kids cause the breeder much
stress.":

Although I realizing we're straying into the realm of the facetious
and the anecdotal, it ought not go unsaid that some studies indicate
that marriage actually increases lifespan. If for example, the
"nagging wife" nags her spouse toward regular medical examinations and
physicals, that can be a positive, life-extending thing.

Well, as the group with the fastest-growing rate of HIV infection is
straight women of color, I don't think HIV can really be making all
that much of a difference.  Gay teenagers do have an elevated risk of
suicide, but other than that, I can't see it being different than
straight people.