We did a 4 week "tour" last year. We set off at the beginning of May went up the west coast as far as Isle of Skye and then back down thro Central Scotland to Edinburgh and then home at the end of May. The roads were relatively quiet, there was space on caravan sites (all CC sites by the way) and the dreaded midges were still in workshops being serviced for their forthcoming assault. IMHO this was a great time to go to Scotland the countryside was coming "alive" the weather was favourable, if at times a tad cool, and the scenery etc stunning.
We have just been back from 2 weeks near Drumbeg ,we had rain gales sunny per periods and it was smashing. Last year in September we were at Glen Elg, first day snow others wind/rain sunny periods, smashing again.Reason is we go for the scenary which is beutiful at these times of year.When we use to go at the usual times such as May and July i can only remember midges and the walk up Ben Nevis in mist and snow at the top.As a complete southerner it is always raining north of Watford so we go prepared, even to the ex wd spade i ues to carry after having to dig a moat around the awning at Glen Nevis campsite. I suppose it does not matter what time of year you go, Scotland has the Rhien, Alps,and history wihout going accross the channel to contend with.
Clubman forgot to mention the fantatastic display of the wild rhododendrons that flower during May a sight not to be missed, you also have the early and late evenings of sunshine, saw clumps of snow on the mountains this May when we up there.Living in Essex its a hell of a journey but its worth it, increased fuel bills have so far not stopped us.
Scotland is beautiful any time of the year, but you have to be prepared for all types of weather, the weather can change from day to day.
The best time for us is middle of May to early June and we never seem to be bothered with midges at that time of year. 2 years running we were having glorious weather on the west coast of Scotland at the end of May whilst the rest of the UK was under cloud.(that was quite a few years ago though)
Just be prepared for anything and you may be pleasantly surprised!!
Don't forget the East Coast, good dual carriageway road up to Aberdeen, then on up to either Banff/Nairn or Portsoy. From Inverness you have Tain, Dornoch, and Brora, even Portmahomack with views out over the Dornoch Firth. Not as dramatic as the West Coast but no midges. Great Golf and not overcrowded. Some real good eating places, enough supermarkets etc. The only downer can be the weather,but that's the same any place you may go.
As a proud resident of Aberdeenshire I would agree with Frank and recommend our region.
Less crowded than the West Coast. No midges. Lovely scenery. Dialect second to none!!
As to the time of year, depends on many factors. Weatherwise May till October can be fair. It is probably quieter during term time, though remember that Scottish school holiday dates are different from the rest of the UK. Though having said that my wife and I are both teachers and have never had too many probelms getting a space on the CC site of our choice during the hols.