I'm not aware of anything too nasty Plymouth side so jump in and see how far you get. Plymouth has Bovisands Fort for a burger and coffee, you can call into one of the marinas and walk into town or use the facilities there.
The Tamar has some great pubs but not sure what effect the tide has and how far up you can get at low water.
You should be able to get over to Looe as well, 14nm from Plymouth (ish) with Plymouth being 24 ish from you. This link will give you some distances you can then work out where to go
Yachtpilot: SW England