I lived in Cornwall for about 6 or 7 years in the 1980s, midway between Truro and Redruth.
The seal sanctuary at Gweek has already been mentioned. The roads all around the Helford River in that area are worth a drive just for the scenery. Sometimes on my way home from work I'd detour to take some of that route just for a change.
It's 20 years since I was last there, but even then Newquay was something of a mixed blessing, often overcrowded in summer and best avoided on bank holidays. Like many British seaside towns though, parts of it become almost a ghost town in winter.
For beaches and the usual seaside fare, there are a lot of much nicer, smaller towns along the north coast. Porthtowan was a favorite for me, as it had a nice beach and was close by.
http://www.cornwall-online.co.uk/carrick/porthtow.htmIf you're interested in communications, you could also head down the Lizard Peninsula to the Goonhilly Satellite Station. When I worked there it was much smaller and pretty much just a "regular" BT installation, but they run all sorts of guided tours and events now. While down that way its only a few more miles to Lizard Point, which doesn't really have much there, but you can claim to have visited the most southerly point in England!
http://www.goonhilly.bt.com/Tin mining was a big Cornish industry at one time. You can take a tour of the old underground mine workings at Wendron, a few miles outside of Helston:
http://www.poldark-mine.co.uk/If you'd rather stay above ground, there are places like the Lappa Valley narrow-gauge railway to enjoy the countryside:
http://www.lappavalley.co.uk/