We booked this bike tour through our hostel in Mendoza. They highly recommended it over the traditional tourist vineyard biking trip - said that on the tourist trip you mainly just get drunk and have to dodge lots of people and traffic. You can have the company pick you up in Mendoza, but it is cheaper to take the local bus to Maipu and just walk over to the company, very cheap bus ticket and less than a 5 minute walk in Maipu to the company.
Baccus has two bike choices depending on how much you pay. We paid about 30 ARG and got the cheaper bikes - which were OK, I am about 5'9" and it was hard to find one that actually fit me. My bike would change gears sometimes without asking me - which was interesting, but honestly for one day of biking it wasn't a big deal, especially since we were drinking wine! If you are picky about your bike, you can pay a little more and get a Trek bike, they have those as well my guess is that they are in a little better shape. As an added bonus, if you decide to purchase wine from the wineries, the bike tour company will send a runner to pick up your wine from each winery - so you don't have to try to bike with the wine in some way (especially after drinking!).
The woman working on the day we came in was really nice - she sorted out bikes for us, and then gave us a map with the different wineries on it with explicit instructions. There were five stops in all, four wineries and one chocolate / fine foods/ liquor shop. Each winery charged around 10 - 15 ARG for tasting. We only made it to three of the wineries, as the fourth was closed before we could get there - we spent a long time at the organic winery having lunch as well as tasting. Each tasting involved a tour of the winery building and a personal guide, with a tasting of the various wines they produce. We noted that we had expected more actual vineyard tours as well - on this tour there wasn't anything like that, really.
The biking route is on village streets in Maipu - so you still have to dodge some traffic. Our group from the hostel sort of had more of a picture of riding around on dirt roads in between the vineyards with the Andes in the background - apparently this is possible, but more in towns south of Mendoza possibly near Malargue. I will repeat - it was still very nice, just not what we initially had pictured.
So - overall, I was happy with the experience, great price, the wines were fabulous, and it gave us a nice day in Maipu. I would still like to do a cycling tour in a more rural area and actually get to tour the vineyards as well as the wineries. If you are looking for a short day that is way better than the traditional Mendoza tourist experience, with wonderful wines and a super reasonable bike tour company, this is your trip.