They're like pretty much any other predator. They eat what they can. A mountain lion with reduced hunting capability due to age, injury, illness, etc. will naturally start seeking out easier prey items even if it comes with the risk of increased exposure to humans. Nuisance predators usually prove to have something like that going on with the exception of foxes, coyotes, etc. that have become better adapted at living close to humans. Big cats are seldom seen for a reason. They generally try to avoid us.