Yes, DOPES is a Scrabble word!

Letter values in Scrabble US: D 2, O 1, P 3, E 1, S 1.

Is it a valid word?

DOPES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

street names for marijuana
an ignorant or foolish person
carbonated drink flavored with extract from kola nuts (`dope' is a southernism in the United States)
slang terms for inside information

take drugs to improve one's athletic performance
add impurities to (a semiconductor) in order to produce or modify its properties
give a narcotic to

Also: green goddess, mary jane, the skinny, low-down, dope up.

Not playable in Scrabble US: SESS, SENS.