Could the Philistines write? Of course they could. They must have been able to write. The question arises because we can’t produce a single specimen that can be identified positively as Philistine writing. We don’t even know what language the Philistines spoke.
We know the Philistines could write because writing was well-known in the ancient world and the Philistines were a great ancient civilization.
Many large caches of ancient texts have been found by archaeologists, and occasional inscriptions are continually uncovered in excavations. Scholars have identified and translated texts in Sumerian, Akkadian, Babylonian, Egyptian, Ugaritic, Hittite, Hebrew, Moabite, Aramaic and Greek, just to name some of the best known Near Eastern languages—but not Philistine.
The absence of Philistine inscriptions is especially anomalous because we know so much about the Philistines, not only from the Bible, but from innumerable excavations where they left their remains and from the walls of Egyptian temples where they are depicted.