The only trips that I know of that are specifically focused on dolphin encounters in the wild are those in the Bahamas and Bimini for Atlantic Spotted dolphins. In most likelihood, bottlenose dolphins will also be encountered on these trips. However, these are snorkeling and freediving only trips, since as mentioned by Roatan Man, dolphins - generally speaking - are not very fond of bubbles and perhaps the sound of bubbles. If wild dolphins is what you want, in my opinion, it doesn't get any better than this.
On scuba diving trips, dolphins are more of a chance encounter, but with that said, there are some places where encounters are pretty reliable.
Besides the places already recommended by others, I would suggest Socorros (Revillagigedos) Islands in Mexico, where I have had excellent encounters with bottlenose dolphins on all three of my trips there. Socorros is better known for mantas and sharks, but the dolphins there are quite diver-friendly and seem to seek out human interaction.
The dolphins in Cocos used to be a bit aloof, but maybe because they've gotten used to seeing more boats and divers in recent years, it seems to me that on my most recent trips there, they have gotten diver-friendlier and don't scoot the moment that you try to approach them. I wouldn't go to Cocos strictly for dolphins, but if you had always wanted to go there to see all the other big stuff, then maybe the dolphins would be a nice bonus.