The best water you will find is in Idaho (Selway, Lochsa, Snake and Salmon Rivers). (Un)fortunately, to float self-guided, you need to submit an application (by Jan. 31) and hit their lottery. We finally got a Salmon permit this year after 5 yrs. of trying and it was well worth the wait. We've done the Snake a couple of times and it's wild at high water (15k cfs+), especially when your heavy with gear for a 4 day trip, and you negotiate 2 class IV-V's in the first 3 hrs.
If this is more of a 1st-time, "shake-down" float with your girlie, I'd recommend the Deschutes (class II-III), which has good flows year-round, or wait until next spring and float the Grande Ronde. Or pay the $$$ for a guide who knows what they're doing. Even a seemingly tame river can surprise you in a big hurry, novice or experienced alike. Enjoy!
Check H2O flows on most any river at the USGS site.