Haven't done this with the X, but with my old personal BB Tour, I used to head out into the desert areas, or up into the Mountains, take some photos with the BB and send them via email. Many of those emails did not send until I was in the Verizon service area.
So, being that the only difference is the tool, and all emails were via Imap Gmail accounts, I would guess it would hold in the phone's memory until it was sent. Now, the question I would have is will it hold with the unit turned Off? I never turned my BB off, if needed, I plugged it into the accessory plug in the Hummer.
But another option might be a free program called "Catch." You can take photos and then tag a 'note' to the photo. I have played with it once, and I was able to tag a photo with a pretty long note.
Once tagged with a note, you can print it, send it to photobucket, picasa, etc., put it into your 'dropbox' if you have it installed, and/or send it as an email. All this can be done after you re-enter your carriers service area.