Air carrier flight crew awaiting departure at MCO described a runway incursion event when Captain misunderstood the controller's phraseology regarding other traffic.

Narrative

As we approached the [Runway] 17R hold short line; we were aware of an aircraft on about a 5 mile final. The Tower Controller issued what I thought was a 'line up and wait clearance.' My First Officer asked me to stop the aircraft so we could get clarification on the clearance. The Tower Controller told us that we where to follow traffic departing the 18's. I then realized that I mistook the way she used the phrase '18's' for line up and wait. When I stopped the aircraft; approximately six feet of the nose was over the hold line. I did the professional thing and told the Controller about the incursion. She asked another jet if they could accept a landing clearance for 17L and they said no. The Controller issued them a go-around clearance; which they complied with. The Controller seemed to be rushed and was speaking in a non-indigenous dialect that I am not used to listening to. Next time I will stop and ask the Controller to slow down and speak so I can understand the information given. Second; since we were departing 17R I could care less if we were following traffic departing any other runway. The information she gave us did nothing to contribute to safety. The clearance she should have issued; that would have contributed to safety is; 'Company flight number hold short of 17R; landing traffic.'