Portland is a compact city, and public transit will get you to most attractions within its limits. However, if you are planning to explore outside the city--and Portland's greatest attractions, such as Mount Hood and the Columbia River Gorge, lie not in the city itself but in the countryside within an hour of the city--you'll definitely need a car.
The major car-rental companies are all represented in Portland and have desks at Portland International Airport, which is the most convenient place to pick up a car. There are also many independent and smaller car-rental agencies listed in the Portland Yellow Pages. Currently, weekly rates for an economy car in July (high-season rates) are about $188 with no discounts. Expect lower rates in the rainy months.
On the ground floor of the airport parking deck, across the street from the baggage-claim area, you'll find the following companies: Avis (tel. 800/831-2847 or 503/249-4950; www.avis.com), Budget (tel. 800/527-0700 or 503/249-6500; www.budget.com), Dollar (tel. 800/800-4000 or 503/249-4792; www.dollar.com), Hertz (tel. 800/654-3131 or 503/249-8216; www.hertz.com), and National (tel. 800/227-7368 or 503/249-4900; www.nationalcar.com). Outside the airport, but with desks adjacent to the other car-rental desks, are Alamo (tel. 800/327-9633 or 503/252-7039; www.alamo.com), Enterprise (tel. 800/736-8222 or 503/252-1500; www. enterprise.com), and Thrifty, at 10800 NE Holman St. (tel. 800/367-2277 or 503/254-6563; www.thrifty.com).