Lake Lowell (Lake Lull) can be really tough. It's hard to find clean wind out there. And you'll find the carp to be quite a problem once you start foiling. Speed bumps that will throw you off your rig.
The closest decent option is Lucky Peak in the mornings. You can put in at Turner and get blown downwind to Barclay. A bunch of us did that while learning to wing. It's not great because you're in a wind shadow unless it's a very windy morning or you paddle out into the main wind, but it has proven results. You might be able to thumb a ride on a waverunner upwind too. LP blows on clear early mornings when you see east winds forecast on our sensor:
https://windalert.com/spot/93670
It's also possible at CJ Strike as NW wind will blow you to the campgrounds. You can also put in on the west side upwind of Black Sands resort and if you come back before losing too much ground (before the Black Sands resort boundry), it's shallow and easy walk back upwind. Let me know if you need exact map locations
Ultimately, nothing around here is that great and you have to put in the hours or find someone with a boat to follow you. It's not a bad idea to take a trip somewhere for a few days to get things worked out. Hood River should fire up soon and is great for lessons and getting the basics figured out.
Also, if your board is feeling too small and the chop is knocking you off, it's not a bad idea to borrow a really high-volume board for a session or two. Something you can really stand on easily without sinking. I think there are a few in town. These boards are really hard to foil, but will get you standing and schlogging back and forth to figure out wing control. Stick with it! You'll be ripping upwind in no time!
--Will