I own the game. It's really difficult, the graphics are sub-par, the sound track gets repetitive, and they recycle the same enemies over and over.
That being said, buy the damn game. The sense of humor and gameplay alone is worth whatever money you're going to drop on it. It's a real trip back to the day when games didn't need next-gen graphics or orchestrated soundtracks. It makes a great game with just a frantic, insane pace to mash your buttons at and a sense of humor that falls somewhere between crazy Japanese, horribly perverse, and stereotypical American.
Oh, and the gorilla is just a guy in a gorilla suit, whom you can kick in the junk and steal his bananas. The Mexican you're thinking of is Elvis.
If you need one of the rarer 'honest reviews' out there, check out
this. I've trusted these guys' reviews ever since people looked up codes for the SNES, and they call a spade a spade.