[Inziladun]

If I recall ROTK correctly, the reason the Gondorians referred to Pippin as "The Prince of the Halflings" was simply due to rumours that sprang up around him. Many of the inhabitants of Minas Tirith had likely never heard of Hobbits (or Halflings) before, and those that had knew them only as a childish myth or legend. With the apprehension prevalent in the city at that time, it was only natural for wishful thinking to elevate Pippin in their eyes to the status of a leader of a Halfling army that would stand with them against Mordor. It had nothing to do with any respect or fear of his combat prowess.
As for other Hobbits being warriors, that depends on what you mean by the word. If you are wondering if they would ever become warlike, or gain a love of battle for its own sake, I find that extremely unlikely, barring some drastic change in their way of life that required them to fight constantly for many years to stay alive.
If you are asking which Hobbits would be capable of fighting at need, though they loathed having to do so, I would say nearly all of them. Hundreds fought to expel Saruman's Men from the Shire, then went back to their peaceful lives after the job was done.