I'll back paulk's recommendation. In my 33 foot motor-home I spent several wonderful wet seasons(WINTER!) enjoying the coastal rivers of northern California and Southern Oregon(my sister lives in Grants Pass). The Cal Salmon, Forks of the Trinity and Illinois are hard to beat! Not to mention many runner-ups. Better have a full dry suit, etc, but it sounds like you are well prepared in that regard!
I've also enjoyed in the USA 48 in spring the Salt, Gila, Verde and San Francisco etc. Better have a self-support boat. They are an adventure but not necessarily gnarly WW.
And yes, Costa Rica. Probably easier now than when I visited through the Winter 1986. And then there is Chile, NZ and anywhere south of the equator!!!
What are your constraints? Spring break? Student/teacher income? Now those are constraints.
You've gotten some great feedback. I started out open boating and kayaking rivers of the SE. Nothing more beautiful and memorable than the Chattooga in spring(otters/blossoming laurels and rhododendrons and more(phenomenal pool-drop)). There is talk about bending over and squealing when visiting there but that is all Hollywood BS. Speaking personally, I never had too that I can remember(I'd likely remember) and I spent a lot of time through high school and college kayaking, caving and climbing in those, ah, backcountry/"implied backdoor" regions. Now, there was the legend of Elise', the stump trained cow, from my caving, deepest back-country days....... perhaps shared another day.