Seems to me that even if the trolley brought more people to the area, there isn’t much chance of it could add automobile traffic. Just more people at the malls and stores.
Trollies are electric and thus pretty quiet so I’d guess it will be fairly non-invasive.
Would be nice to get a spur into Pacific Beach, though it may prove difficult to wash the puke smell out after enough twenty-somethings use it for the ride home after the party.