Right after we reported last Saturday that there will be no 2-player for San Andreas PC, topics crept up on the forums about the June issue of PC Gamer reporting otherwise. We assumed our information was more accurate and did not cover the story, simply because the information we had was newer. PC Gamer was likely just making the educated guess that there will not be a multiplayer mode but the co-operative mode will stay.
We contacted Rockstar ourselves to get the final word on this, and today we have the answer. The 2-player mode won't be included as "the dual keyboard and mouse set up proved too unwieldy for players and didn't work with the PC version of San Andreas' greatly improved free camera mechanics. Rockstar North decided to focus on maximizing the
single player experience." For more about the PC version, read the San Andreas PC & Xbox information page.