Answer: sisisenor

AnswerCrossword Clue
SISISENORSylvester's least favorite Spanish agreement?
SISISENOREmphatic affirmative, in Acapulco
SISISENOREmphatic south-of-the-border assent
SISISENORA south-of-the-border assent
SISISENORAcapulco assent (and a phonetic hint to four of the Across answers)