Hi Mark,
Dogs are welcomed at the F & H although some of the beats have cows and sheep on them from time to time. The beat out back of the hotel is perfect though and probably one of the prettiest along with the beat below which is usually fine for dogs too.
If you are down from the 3rd week of May you should take a look at the Taw as mayfly as been really good the last few years. We rose the first fish on 1st May and the same guy hooked the last fish the second week of June although we did rise a sea trout to a mayfly in July as there were still coming off. It's not like the chalkstreams but there are enough your fly doesn't get lost in a cast of 1000's!
You should be fine on Dartmoor especially if you are heading off the beaten track.
If the weather is poor you and you want to fish stillwaters there's Fernworthy that dogs should be fine at and if you fancy a slightly longer drive Colliford is a great place to fish that you'll be fine with a dog. Pack your tadpole patterns just in case!
Give me a shout if you need anything as I be happy to help.
Pete
Eat, Sleep, Fish #2 out end of Jan