We're gonna go with the time skip. More of us prefer to get right to the action, so anything people want to mention about their time during the time skip they can just write into their next post.
Ti-Nung-Cha does have a point about a caravan would probably be the most inconspicuous way to get all the uniforms necessary, as long as they took over the exact same route to not arouse suspicion. That probably wouldn't work in conjunction with the prisoner plan, though, since most caravans don't concern themselves with that. Another route I was planning on was sort of the "Star Wars" route of jumping a patrol and essentially taking their route back to the prison. There is at least one variety of Fire Nation uniform that covers the entire face (they were seen more in the first season, but I think are generally used to signify firebending soldiers as opposed to non-benders), and those would be the best ones to go after. It'd be much harder to scrutinize the patrol if their faces are totally obscured.
We don't have to worry too much, though; if Sokka can get into the most heavily guarded prison in the Fire Nation, we should be able to get into Ba Sing Se's. XD
Because I'm itching for a little action, I'd like to jump a patrol. That said, I think jumping caravans of supplies for Fire Nation soldiers would be a nifty way to stick it to the Fire Nation Man, so to speak. It's something to keep in mind after we've done the break out.
For clarification, the Dai Li are currently under the employ of the Fire Nation. Azula's show of power was enough to make them switch their allegiance. They are definitely not our allies right now. Those guys are kind of jerks, really.