Ok, just an observation:

The cowboy told Adam that if he hires Camille for hte movie, he will se him <----(cowboy) once, but if he doesnt, then he will see him twice, right?

Ok, so i read a lot of theories and none of them explain the cowboy part, so my theory is:

OK, first of all you need to think something, almost at the end of the movie appears the cowboy, but Adam didnt see him, he is facing the other side, so how do you can take that?? as if he sees the cowboy, or as if dont???

Ok thats my observation, ill hope you can help me.

Another thing: sorry bout my english, ill hope you can understand well

Thanks

Read this explanation: I think it's the most accurate one out there. It implies that the cowboy is merely present in the series of dreams. Whether he knew Adam or not prior to meeting at the ranch is irrelevant because it's a dream.
http://www.geocities.com/mazzyboi/mulholland_drive_explanation.html

5 churchmisters did march along a strong neat little bridge and nthen fast as they came did vanished into a puffee of tinklie dust. \pardon my tone but there is a lama currently eating a rather lzgrge portion of my otherwise well functioning brain. I cant quite type anymorrrrrrrrrrrrr