Pasta dish in Downtown San Diego
Cucina Urbana (Bankers Hill - very close to Downtown) is probably your best bet, but make your reservation now as it's a hard one to get into on short notice. Plus all dishes are under $20...
Bice (in downtown in the Gaslamp) has some excellent pasta dishes as well - the homemade buckwheat pasta with chard is amazing.
Bencotto (in Little Italy - close to downtown) is also talked about, but I've never eaten there so cannot give judgement.
But since you're on Park Blvd - where you really need to go is Pizzeria Bruno - very traditional pizza napoletana - I know, it's not pasta but it IS a revelation.