First off I would like to thank all of the moderators and regulars in all of the Navy threads on this site. The amount of time you spend here responding to every single posting is amazing, and those responses have answered countless questions of my own. So thank you.
That being said, I will give you some of my background. For the past three months I have actively been trying to enlist in the Navy. I've spent countless hours online doing research, made reading every post on this site a daily ritual, and dont think my TV has left the military channel in all that time. So now after three trips to MEPS, obtaining all of my legal docs that were needed, and covering up my pinup girl(heartbreaking), I appear to be close to signing. I go into MEPS next week to process, and am hoping they have a job for me when I go. Although I realize that may not be the case.
Due to the lack of jobs right now my recruiter informed me that by volunteering for sub duty I may have a better shot of getting in quicker, as those jobs come available more often than others. So I guess my first question is how valid is that statement?
Secondly, I have been thinking about trying to get into the SECF field as an ET. I've been doing some research on various ratings on subs, but everything I've found has been pretty vague. So my question is are there certain ratings that would be more desirable than others?
Finally I guess my major concern is that sub duty was more of just an after thought for me, not something I've been wanting my whole life...I realize its not for everyone, so I was wondering if anyone had just general advice regarding life aboard a sub and becoming a submariner.
Thank you in advance for reading and for any responses.

First, you will probably get more answers in the sub forum. You probably should do some reading in there also. Several people, including me, have written extensively on what life on the boats is like.

As to not having always wanted to be on submarines, don't feel bad. A good number of people never think about subs until a recruiter or classifier mentions it to them. I wanted to be a nuke but didn't meet the educational qualifications at the time. The classifier recommended that I volunteer for subs and then try to go nuke when I met the educational requirements. I had never considered subs up to that point, although they always fascinated me. Once I got there, I knew that subs were where I wanted to stay.

On the SECF side, keep in mind that this pipeline produces three ratings. In addition to ET, you could also become an FT or STS.

None of us can advise you on which rating is more or less desirable than any other. That, to a large part, is definitely dependent on you and what you would like to do. I would not have liked being an MM or SK and thought that I would really like to be STS or ET but I ended up being a YN and enjoyed my life as that. As with every other rating on subs, it was challenging and kept me very interested.

Unless you go nuke, there is a good possibility that you will be waiting a while before you go to boot camp. SECF needs people but they have to slot people into boot camp based on availability of positions in the training pipeline.

I had never thought of subs until getting to MEPS. It was brought up as an after thought by the MEPS people ("Oh, by the way, we have subs, too....wanna volunteer? You can un-volunteer later...)

Nver been happier to have made a decision on the fly. It's extra work, but to me it was well worth it.

Thanks to both of you for taking the time to reply. I really appreciate your advice.