Rent a bike and take to the trails
Healthy Ride rents bikes for $2 per half hour. Grab two bikes and explore the Three Rivers Heritage Trail, which has plenty of spots to stop and make out.
Sports often have a high ticket price, but not in the minor leagues! Minor league baseball is some of the best -- check out the Washington Wild Things for $5 a pop.
Buy all of the meats and cheeses for a picnic for two
Browse the cheese at Pennsylvania Macaroni Company in the Strip District, and then head over to Parma Sausage to get your meat fix. Pack up your finds and picnic by the river. Allegheny Riverfront Park, by the Convention Center, is a quaint spot to feel all of the feels.