Yes! You can make as many cups as the product tolerates. For example, the 3 cup espresso maker, if you push the limits, you can get up to 4 cups. You can always remover water and make less cups--as needed---. Just be sure that, if you remove water, to also remove coffee; unless you wish to make really strong coffee--which would be my case! At any rate, you can play with the amount of water you add to the product and the amount of coffee, too. The valve will remove the excess water as the pressure rises while heating ensues. If you have any other questions about the product, I'd be glad to let you know my experience with it--I have two of these wonderful machines.
Espresso "cups" are two ounces. So the 6 cup model makes a max of 12 ounces. You can adjust with less water for strength changes or yes, less water and less grounds for less coffee. I own 3 different size moka pots depending on how many people are having coffee.
When you make less coffee than a full pot, the puck seems to still form pretty well and the flavor rounds out pretty much as a full pack. I tend to not use it so much as an espresso maker but my normal morning has about 3/4 of the hopper with coffee, water up just below the escape valve and it makes a nice full-flavored, large mug of coffee. For espresso (I normally use my LaPavoni for that anyway), I've had pretty good luck packing the coffee tighter and not letting the water get all of the way to full steam vapors at the end of the brew cycle. If allowed to go to the full-steam end, it seems to extract acids a bit, putting a bit more bitterness into the result than I care for. Great little rigs that just plain work, but in my usage, it's more handy for that single, full-flavored morning mug. I think it's versatile enough for you to make partial pots with very little given away for results.