Les Olles, about 1 k from L'Ampolla is dog friendly. Basically you go into the town, head right along the seafront ( ie. by car ) keep going until the road turns into a dirt track and park at the end where the track terminates. The locals all walk their dogs here and it is great for swimming too. There is a shop/cafe and a seafood restaurant and you can visit Bassa De Les Olles lagoon which is just behind the restaurant and small play area.  There are some nice flat walks and it is also popular with cyclists. Have a great time if you go!