Torquay: this is on the English Riviera, a warm, sunny bay on the south coast of Devon. From here you can visit Dartmoor, one of Devon’s two National Parks. There are regular trains from Torquay to Exeter - at least hourly, and often more frequent and it takes less than an hour.
Plymouth: although Exeter is the county town of Devon, Plymouth is the largest town. It has a rather ordinary city centre, but the harbour area is beautiful with an old Barbican and the National Marine Aquarium. It is well-placed for journeys into Cornwall, including visiting the Eden Project. Trains run approximately every half hour and the journey time is about one hour.
Taunton: this is in Somerset with access to Exmoor National Park and the stunningly beautiful North Devon/Somerset coast. Trains run regularly approximately every half hour and the journey time is half an hour.