Newtown Ferrers/Noss Mayo is lovely, but not exactly far from Plymouth!
I like both Dartmouth and Salcombe as places to sail into, although prefer Dartmouth ashore. I suspect you haven't got the time, but I like the trip up past Salcombe to Kingsbridge, or past Dartmouth towards Totnes.
Torquay was quite a nice little stop over, and I really liked Bridport/West Bay for some reason.
Check the tides/weather for Portland and decide whether inner passage or going outside!
Hope you have a good trip!