The Glencoe / Fort William area area is pretty easy to get to by public transport, there is a good range of hostels, bunkhouses, and campsites. Oh, and great walking!
Throughout the Highlands you'll find that getting to the "major" centres by public transport is not too bad but getting around to the trailheads and back to your accommodation can be a bit tricky.
Hence I 've suggested Glencoe - you can walk into the glen from the campsite (Red Squirrel) near the Clachaig Inn (food and beer). There is a reasonably regular local bus up to Fort William and there are always other walkers to potentially hitch a lift further afield.
Skye is also a possibility - although more remote there is a good regular bus service forom Glasgow passing the campsite at the Sligachan hotel, which does breakfasts and evening meals. No shop there tho...
The walking available from Slig is superb, but the mountains need to be treated with respect and call for experience (as they do everywhere in the Highlands, but here especially).
Enjoy!
Ian
www.mountainfreedom.co.uk