Playa Santiago is the warmest resort on La Gomera although you should be fine anywhere in April. San Sebastian has more restaurants and good beaches, Valle Gran Rey is great although a little more touristy. Not greatly so on La G thankfully. I agree about the hippy vibe but I have never found them a problem.
Hiring a car is a great option. Driving is painless here with little traffic, no parking fees or traffic lights. That is assuming you don't mind the windy roads of course. If you have a car then San Sebastian is a good option and you could maybe consider the parador which I would book on a B & B basis so as to experiance the local eateries. I am not aware of your age but if over 55 the Paradors do offer discounts at certain time sof the year at certain venues. Ask if the offer 'golden days' yes I know its a corny expresion but 30 % or more is not to be sneezed at!
Good luck!