It's really difficult to predict what the weather will be like in late October - you could get anything from pleasant temperatures with light winds and sunshine, to driving rain, icy terrain or a little fresh snow on the summits. Statistically, it's the wettest time of year, and high winds and fog are also likely. Having said that, if you're here for more than a few days there's a good chance that at least one of the days should be OK.
If there's good weather with no lying snow or ice, I think I would go for something like Ben Lawers & Beinn Ghlas (2 for the price of 1), Mount Keen or Schiehallion. They all have a reasonable path, except for the top part of Schiehallion which is very rocky.
As others have said, it's worth remembering that there are lots of equally worthwhile, smaller hills which aren't high enough to be Munros, such as Ben A'an, Ben Ledi, Ben Vrackie, Arthur's Seat, Creag Bheag near Newtonmore, Ben Rinnes, Bennachie... (you haven't said which part of Scotland you'll be visiting - these are dotted all around).
jmarkb wrote:LobeyD wrote: There is a 'bad step' on the ridge but it is quite far along and can be bypassed easily
The bypass path is not very obvious when approaching from above (i.e. going anticlockwise). If you find yourself at the steep scrambly section, go back uphill for 20-30m and look for a faint path heading off to the north (left looking up). Erosion has made scramble more unpleasant in recent years and is well worth avoiding - I have seen folk in various states of unhappiness on it on all the last few occasions I've been there.
I agree with this - the bypass for the "bad step" on the Tarmachan Ridge is not obvious from above. Its northwesterly aspect also makes it prone to ice following rain and a cold night (certainly possible in late October). We did the ridge on a sunny day in mid April. Despite there being no ice anywhere else on the ridge, this section had a coating of clear ice which made it quite a challenge - the sun hadn't got onto it even by lunchtime.
Once safely negotiated, we looked back and saw the much easier bypass path...