If you poke around a little on the WDFW website, you will find a section about alpine fishing and a link to a list of lakes and what types of trout are planted there. This would be a good start.

One thing to remember about alpine lakes, you never know what to expect until you get there. I've been to some where we got fish literally on every cast, then a few years later, you can't find a fish on that same lake. Could be because of winter kill, poaching\over harvest, bird predation, or whatever. Also, some lakes have a population that is able to reproduce nicely in the lake - others rely strictly on stocking. If the lake is over due for stocking, you may find slim pickings - if it has been stocked that year - you may find hot action. (edit - actually they tend to stock these lakes with fry - so they need a year to 2 to grow to any size).

When I plan an alpine trip, I try to find a hike that I've either been to before, and have had luck, and\or find a hike that you can set up base camp at one lake, and have several others within a few hours hike to try if base camp is dead or slow. A stream nearby is a cool alternative too (if legal).

There is a good book out that covers fishing alpine lakes\streams located off of I-90 (same guy did a book a while back on fishing for trout in the Olympics). I found my copy last time I was at Creekside angling in issaquah.

Good luck this summer!

By the way, a light weight trout rod (spinning), casting bubble, and a mix of dry flies, terrestrials, nymphs, and wooly buggers work AWESOME in most high lakes. You don't have to pack a float tube, and don't have to worry about a back cast...

-Chad