Fur Finley is right on point. His answer is perfect. Go with the 143.

First, a 143 would be perfect for you. My wife weighs exactly what you do, has a 143, and loves it. Plus, the size charts match up for this size too.
Because you are a beginner I would definitely recommend you have a board that is on the smaller end of the spectrum. With it being shorter it will be so much easier for you to control and maneuver.
And yes this would be a great all mountain board. It is designed for "all mountain" so you're good to go no matter where you go and what you try.
Also, just so you know, it is a directional board, which means one binding is closer to the end of the board than the other. Meaning you want the side that's closest to the end to be the back of your board. This way you will float over the snow easier.
You'll love this board. I ride a Forum too, and I love it!

thinking too technichal. i'd say 146 and nothing higher or lower. the 152 will be a bitch for someone 5'3" to pull. and the 138, although 123lb is in its range, its not practical.

how much do you weigh? if your over 105, ride a 142. 138 is going to feel like your feet are strapped to nothing

I would go with the 138 or 142. Your board size has more to do with weight and skill level and in your case foot size, than height. A smaller board is for a lighter rider and/or for park/pipe use. A longer board is for a heavier rider and/or for all mountain, carving, back country, etc. Smaller boards are lighter and more manueverable (easier to control), but longer boards float on powder and are more stable, especially at higher speeds. If you are a beginner, go for the 138, it will be easier to learn with, then upgrade to a larger one when you get to an advanced level.

ps. do not get the 149 its WAY too big!

for this board a 143, I'm 5'3" too and I ride both a 140 and a 146, dont get a 140 or lower i felt the board was too light (i actually broke it a month ago). the 146 was tough to pull in the beginning because I weighed like 99lbs when i got it but now im like 107 and its not bad( - a little long i feel its not good for pipe.) but if you weigh more it will be more ideal. i'd say go with a 143 the perfect medium. (ps-we have the same size shoe, any that doesn't matter with ur board size unless ur feet r gigantic, that only helps deciding your binding)

You could get the 149 if you're going to be riding more all-mountain w/ some powder riding in mind as well but you could get the 146 if you're into more park riding.