Was wondering how many levels players aare assigning to this skill? Is there a cap of some sort as to how high the ekill can go?

I've only played through the series once, but I didn't assign a high priority to Cartography. I started with it very low, and only put in more points later on when I had points to spare. 1 is the minimum you need to have to draw some sort of map, but it is very bare bones and it will require you to remember many features yourself. 3 will draw you a passable map so you're able to see all the important features. Higher than that is mostly just to make your maps look more pretty (especially 5 where it will draw water and roads in different colours). I believe 16 is the highest level (I never raised mine that high).

If we're talking Book 1 I was quite annoyed when I payed the trainer to get me to level 4 when it painted a green background everywhere, even on the water. By now my character is at level 8 and I'm happy with the results.

For character creation, unless it's your very first game, I wouldn't assign any points to cartography. You don't need a map to find that sextant and if you build your character right you can defeat those thugs at level 3.