We paddled the Upper (Class4/5), and Lower(?), Class III Diable last spring at around 60cms. According to the book that is flood level, but it was still within its banks. I really enjoyed it at that flow.
The Diable is the river that flows right though Tremblant. Keep driving past the parking lots and you’ll see it on the right. The put in for the Upper is at the lake you see through the trees at one point, and the put in for the lower is a well marked pull off parking area at the top of a hill.
Not the best directions, sorry.
There are lots of rivers in the Tremblant/St Jerome area, and you should try to translate the book – ot will likely be better than the advice you get here!
Phitty’s right, the Diable is good fun, the upper definitly has some challenging whitewater.
There are tons of rivers around there – the earlier it is in April, the more concerning ice around the rivers becomes. Also, some of the better runs in the region will be fairly significant class IV and V when they’re high at the start of April.
Get the recent French guidebook – if you can’t read the info, the maps will at least get you to the putin and takeout, or hook up with someone who know where to go.
The book is not available in English (to my knowledge), but even if you don’t speak french there’s good maps of each river, with put-ins, take-outs, hazards, descriptions of named rapids at different levels, etc.. that you’ll find pretty useful. I think the book has about 100 different rivers in it with about 150 different runs.