Green’s Dictionary of Slang

Pedro n.

[Sp. name Pedro, Peter]

1. (US) any Spanish-speaking person; also attrib.

[US]Maledicta II:1+2 (Summer/Winter) 167: Pedro Any Spanish-speaking person, used primarily in New York City, mostly in reference to Puerto Rican immigrants.
[US]G. Pelecanos Night Gardener 268: ‘I’m not having no Pedro food,’ said Henderson, speaking of the papusa place.

2. cocaine [ref. to S. American origins of cocaine].

[UK]K. Sampson Powder 87: ‘Do you know Pedro?’ [...] ‘Alas, I know him well.’.

In phrases

friend of Pedro (n.)

a cocaine user.

[UK]K. Sampson Powder 369: Between drug buddies – Friends of Pedro – it was unforgiveable.