Tricky, but I’d suggest you go for intermediate.
I went to a whistle class last year, and we only had one stream. As a result, we ranged from people who had never played any instrument before, to people who had played quite a lot, and just wanted to practise technique and learn tunes. I fit in somewhere in the middle.
It also depends on how the guy is running the class. After my experience, and if I were competent to run a class, I’d aim to do teach two tunes a week maximum, one fast, one slow, for a ten week course. I’d do a 3 tune set, one tune per week, so by week 4 the students should have 3 slow airs, plus a 3 jig set, all of which they should be able to play without mistakes, if not at top speed.
Weeks 4-6, do a 3 reel set, and keep playing the jigs & airs, gradually upping the tempo on the jigs.
Weeks 7-9, maybe 3 polkas. So by week ten, the students should have three 3 tune sets, plus various slower tunes. This gives them the feel for reels, jigs & polkas, so they could tackle other tunes they come across with better hopes of getting the right feel.
On top of all this, is the guy going to use ABC, sheetmusic, or some other notation, or just learning by ear? As mentioned by Brewerpaul above, you should be able to record the whole class and playback at home for practise. Minidisks are great for this, as it’s easy to just set the thing going, record the whole class, and then edit out the unwaneted bits later.
The danger of joining too high a level of class is that you might annoy the other players by being too slow on the uptake. Generally, if you practise enough between classes, this shouldn’t be a problem.
You’re better off aiming high & stretching yourself than aiming low & getting bored.
My 2 pence 