Yep!  Moles are your friends!  The reason they like lettuce patches is that slugs and snails like lettuce!  They also aerate the soil but they make lawns look a bit messy and unkempt, which is all right with me, but people with golf course lawns don't like them at all so they go around poisoning the wee things.  Of course they usually pour so many chemicals on those kinds of lawns that the mole poison is the least of the worries.

I also have some stones and cracked pots in the corners of my garden for toad houses, because toads eat slugs and insects.  Try to make friends with your garden carnivores!  (you can also buy 'toad houses' at garden stores, but my toads seem to like half buried pots and flat rocks set at angles just fine!)

Rabbits and deer like lettuce, and it's amazing what a few slugs can do over night in a lettuce patch.

Well now, woodchucks DO like veggies, but they don't like to be too awfully far from their holes… hopefully you don't have any especially bold ones, and I suppose moles could damage the roots of veggies with their tunnels, but really I've never had that much trouble with them.  Deer can lean on that plastic fencing and push it down enough that they can reach plants, but you'd probably notice that so it doesn't sound like that's your trouble.  I vote on wascally wabbits and maybe some insects too.

As far as which way lettuce patches should face, that can depend on so many things, but lettuce doesn't like extreme heat, so morning sun is good, but not too much afternoon sun.  I can only grow a very small patch of early crops here since I live on a hill, surrounded by woods, but when I had lots of room, I planted in wide rows (2 ft wide), sort of an adapted square foot style.  things like lettuce in blocks filling a 2 ft square etc and staggering bigger plants in the row so I fit more plants in that way.

I'd look at the way the sun traveled, and make sure I had the fat rows going east to west, so the sun traveled along the rows.  That way, tall crops didn't shade lower ones and everyone was happy.  There are so many ways to do it though and it has to make sense to you.

An early crop of lettuce, with some green beens down the middle is good too, by the time the bush beans get big enough to shade the lettuce out, it's too hot for the lettuce and it's going to seed, then the beans take over.  Then a later patch of lettuce in an area that is doing poorly, and the lettuce starts when it's hot, but is at its prime when the weather is cooling off.

My gardens are never the picture perfect kind, but I usually got goodies spread out over the season very nicely.