I'm putting this together as I go along, so I'll add to it as I find stuff:
In May 1943, the 12th AF were based on north-west African bases for Operation Husky and during the course of this, destroyed in the region of 1,000 Axis planes. The 12th then dug in on Sicily and continued the air umbrella into Italy.
The 12th AF comprised three FGs; the 1st, 14th and 82nd and these were supported by the 3rd PRG.
Most of the P-38s in-theatre at this time would have been P-38G-10s or -15s.
In November 1943, the 15th AF was formed in Italy, with the Foggia airfields being its principal home. All 12th AF P-38 FGs, the 1st, 14th and 82nd were transferred into the 15th, along with the photo recon group.
Missions hereafter switched to the support of Anzio, comprising strafing and dive-bombing. Route into and out of the target area would have been across Italy to Naples, out to sea and up the coast to Anzio, reciprocating the course on the return leg. I haven't found any mention of 12th or 15th AF presence on the ground in Naples itself.
During February 1944, the 15th coordinated with the 8th in the UK for attacks on Germany, the long-legged P-38s took this in their stride, even from Foggia.
By this stage (late February), P-38Js in the form of the P-38J-15 were beginning to arrive.
The P-38J possessed the flat, bullet-proof windscreen, not apparent in your photo so I would suggest one of the earlier models mentioned, variant of the P-38G.