Maggie,

The Glen Hotel's website has the published rates.  I don't know if you've seen it or not:

http://www.glenhotel.com/Default.aspx?tscategory_id=1

It looks like 55 euro is a much better deal than the published rate.

As far as Altan playing in Teelin .... well they used to own a pub there called Cul A Duin pub and I guess a couple of years ago while they were kicking back for a bit they would show up for sessions occasionally but they've sold the pub.  They've also recorded a CD around that time called Local Ground.  However there are still music sessions there on Saturday nights as I understand it but without as many famous folks showing up.  Its a shame because I've heard it was awesome pub to go for a session on a weekend and I was hoping to get there either this year or next.  Maybe it still is good ... only one way to find out.  I'm sure once you get into the area and ask around you'll find out where sessions are going on.  Maybe pubs like Roarty's or Biddy's in the Glen or Cul A Duin in Teelin.  

What I can tell you about the town/area is first of all it is a place of incredible, natural scenic beauty.  Hauntingly beautiful.  Very, very friendly people although hard to understand because of their thick accents and of course Gaelic.  I'll never forget checking into the Glen Hotel and opening the window of my room and looking out at a flock of sheep grazing on the hotel grounds and looking across at the misty, green rolling hills dotted with sheep.  Truly Ireland at its best.  I also remember the feeling of crossing over some sort of invisible barrier as we came into the area as if we had just driven back in time.  You sort of go up in elevation through boglands with barely a house as far as you can see and then you come into this green, misty valley with cliffs and ocean.  That's Glencolmcille.  I lack the writing ability to describe it so I can't do it justice.  You'll see.

Mark.