Cars work best for navigating the New Hampshire seacoast region. Highways are well maintained and convenient, though the summer months see a major influx of tourists and congestion on I-95 occurs frequently. The cities in the region experience moderate traffic, except for the beaches during prime times such as early afternoon, which get very crowded.
Portsmouth and surrounding areas are serviced by a free COAST (http://www.coastbus.org) trolley during the summer and fall. The trolleys are convenient and make many stops in the area.
The city of Portsmouth is small and the major historical points of interest are easily visited on foot. Most downtown establishment will have one of the free local maps available that make touring the downtown on foot easy. You could also walk along the Portsmouth Harbor Trail (http://www.portsmouthnh.c...).
Bicycles are also a very effective means to see the area, see the Seacoast Area Bicycle Routes (http://www.seacoastbikes.org/).
