Cover it with crew-height socks. For one thing, those socks are typically more comfortable (less chance of being bitten by bugs and then having your shoes rubbing on the bite, anyway). I have six tattoos and never once had a problem with covering them. Most are covered by a regular shirt, but one's on my mid-calf and another's on my right wrist. For the one on my calf, I had the "option" of wearing pants, but I covered it with large band-aids until my manager busted me. For the one on my wrist, I wore a watch with a wide face (it's shaped in such a way that a watch can easily cover it). It is possible to hide them, you just have to be vigilant about it.
If the socks don't work out because of the height of your tattoo (which it doesn't sound like that would be a problem), I'm sure you could wear pants. Any role that has shorts as an option also has pants, for cooler weather. I'm not sure about skirts, though. From the costumes I can remember that had skirts, most of them came down to mid-calf or lower. I don't remember if any of them were shorter than that.