YES!
although I try to work out at least every other day. I have a friend who works out with me only 2 days a week, he went from benching 130 to 200 in like 3 months... this is of course, if your goal is to build muscle mass. If you want to tone, you're going to need to work out more regularly... If you want cardiovascular fitness, riding the bikes/running on the treadmill 2 times a week is better than nothing...