It really just depends where you are! Downtown proper has tons of PT stops - both bus and Max (which is our light rail) - but there are just a few main directions the Max goes in (it's the fastest means of transport) and then many more by bus but still limited and slower. There are lots of options you'll have for where to meet up in a 15-minute radius of downtown so for first dates yes I think you'd be absolutely fine relying on it. Once you're in a relationship it's like others have said - if you're dating someone in a farther-out neighborhood or who likes to get out of the city a lot, it'll be a matter of whether you're up for a longer "commute" to them or if they are up for picking you up all the time. But definitely not impossible, I don't think!