heh when are you going? i am going 4th march, done a couple of ski seasons, so might be cool to meet up and get a pisten bully with a few others to do some off piste stuff
Yastrebets 3 is by far the best run for boarders, there is a chair to the top, so no larking about with drags. There is a good jump at the junction by the cafe, definately my favourite run.
The best boarding runs in Borovets are from the top of the Gondola down Yastrebets and back up the 4 man chair lift at Yastrebets. There are several routes down from the 4 man chair.
Definitely a good idea to avoid the button lifts - i only managed to get up halfway on a green run, then got off and walked the rest!!
I was only learning but the other people i went with in my group said the runs from the gondola were the best - there's plenty of choice, especially wide runs for practising turns.