The Delaware is the best local smallie fishery to Nazareth IMHO. Remember, you can fish any shore with a PA license and you can hit some spots better from the NJ side.
I would agree the Delaware above Dingman's Ferry is fishing better lately, but I suggest you get to know spots closer to home. The fishing is good, but not non-stop action. North of Easton/P,burg is decent. The rapids above St Anthonys Nose/Marble Hill is good. I think the NJ side access is better but can park at Frost Hollow access off 611 on the PA side. (not much access from 611 in this area IMHO - but maybe you can find some). On the way to Belvidere there are some good spots from the PA side. All around Foul Rift rapids can be good - can walk down from Riverton Ball Fields or from environmental center. Doe Hollow has good fishing. I like upriver in the rapids for fly fishing, but anywhere along the drop offs will have fish. May have to compete with boats though. I would suggest scouting out the local river so you have spots to fish if you don't have much time.
If the Delaware seems big, the lower stretch of the Brodhead from the paper mill down has smallies and the big hole by the gaging station has every kind of fish that is found in the Delaware, but some of it is hard to fly fish.
Haven't fished the Lehigh in a while, but may be some good options there. Can shoot right down to Bethlehem from Nazareth and get access from one of the parks along the river.