Just wondering what the most efficient frame size is for a bike? I'm 5'9" with kinda short legs. Thanks.

There are many sorts of bikes, traditional road bikes, compact road bikes, mountain bikes, hybrids...you need to visit two or three first rate bike shops and get fitted for the type of bike you intend to ride.

One basic rule of thumb:

- When you stand flat footed over the bike, just behind the stem, there should not be uncomfortable contact with the top bar

Other than that, you can get a better fitting at an LBS than on the internet.

I am almost 5' 10", with a 35 inch leg length and wear 32 inch slacks. On a traditional geometry road bike, the bikes that fit me best are between size 57 and size 61...but traditional geometry bikes are no longer in the majority.

Go to www.wrenchscience.com and see what frame size comes up when you enter your information.

If you have a short standover and long torso then you need a bike with a higher length/height ratio.
Some trad frames can be found in longer forms(such as Lemond).
Generally, such riders go for compact style frames where standover clearance is never and issue and you select on the basis of length.

Go to your lbs and see what they say. A compact will be different from a classic geomerty.