Portland is a streetcar city. Everywhere you go, you will find streetcars. You can go to most places with streetcars. I didn’t use bus except once at late night.
There are two kind streetcars in Portland.
1. MAX: https://trimet.org/max/
MAX is operated by TriMet, operated by the state, and also operates buses. Trains are larger than Portland Streetcar, and mostly runs in the center of downtown area. Many lines also go to suburban including the airport.
2. PORTLAND STREETCAR: http://www.portlandstreetcar.org/
Operated by the city. It circulates around the city or runs west side of MAX in downtown.
Only the difference between two for tourists is MAX’s one-way fare is 50 cents higher ($2.50) than Portland Streetcar ($2.00). Portland Streetcar honors all type of MAX tickets. I suggest you to buy one day pass at station vending machines of either MAX, Portland Streetcar, or MAX smartphone app because it’s only $5 and available until 3:00 a.m. One day pass is also good on TriMet buses.
TriMet Mobile Tickets app is probably all you need to get around. You can buy tickets or passes instantly, and just have to show it whenever asked by operators (if you use buses, just show a pass to drivers). You can also search upcoming trains or buses with this app.
TriMet Mobile App: http://trimet.org/mobiletickets/index.htm
There are also convenient smartphone apps, such as real-time arrival tracker. Check this website and find out your type of apps.
I used “Arrival Tracker”, the third app because that reflected Portland Streetcar also.