Jock, the attack started April 17, 1797, and lasted until the Spanish forces--which were mostly criollos (native-born Spaniards) forced the British armada to retreat on April 30th. Perhaps as a consequence, no other major assault of New Spain was attempted. I had seen examples of the uniforms worn by the San Juanero forces on display at El Morro, the massive fortress built at the tip of the peninsula which guards the Bay of San Juan.

It was on this same campaign that Abercromby seized Trinidad and Tobago for the British Crown. One consequence for him was that, upon his return to Britain, he was named commander of the Royal Scots Greys.

P.S. Most of this information is courtesy of Wikipedia.