How about English (spoken) with the following drop down values:
Native speaker
Good
average
minimal

Now when she speaks no French, Greek or Russian, THEN we have a problem. lol

I have been with hundreds of women who barely spoke a single word of English, some of them were off the chart in the sex department.

I don't think this is a critical component to a good session. Does it help? Sure, but I've had a few sessions with some gals who had very little English and we got along just fine. I mean isn't communication 80% non verbal?

For example, if she can't understand certain directions in English it really slows things down.  i.e., I don't want to have to physically guide her into a new sexual position.  I also like to joke around to lighten the mood, tell her how hot she looks, or whatever.  If I can't do those things, the session is lacking.  If none of this bothers either of you, fine.  But for those of us for whom it matters, it would be nice to know.  If I had the choice of two equally hot women and one spoke no English while the other did, I'd certainly choose the latter.
Bottom line: the more information the better, and knowing her language skills certainly does no harm.

Absolutely.  
At my age I don't go in there for one hour of straight sex, and it is nice to be able to converse a bit.
It just adds to the whole experience.

Most of the time this is mentioned in the reviews... so why add more clutter to the profile?  Unless... you want to be able to search by this category... which I suppose would be a good thing.  I just wonder how much the demand for it would be.

How about:
Language(s) spoken with drop down:
Native - list here
Fluent - list here
Good - list here

while the info would be useful, I actually find it oddly hot to have to figure it out without a mutual vocabulary.  

Because as much as I know he likes to fuck, There is no one I know who likes to talk anymore than mister "keyboard diarrhea" himself,  and as a blabbermouth myself, I feel quite qualified to speak on the subject. lol