Thank You, Tax Refund

So... what do we need to know about traveling to Portland and the nearby coast in mid June for 9 days? Figure we'll spend 3-4 days in Portland, then take off for the coast, explore a bit (maybe go to the Olympic Peninsula? I've always wanted to see a temperate rain forest). Thoughts, suggestions, heckles, from the Oregonian crowd? We'll probably fly in, use public transit in Portland and then rent a car for the coast trip. Any pitfalls about renting a car in Oregon I should be aware of?

Thanks in advance for any suggestions! (oh god do we need this vacation)