Heat a large skillet over medium-high heat.
In a small mixing bowl, combine goat cheese and guava jelly until just blended (little bits of cheese and jelly are a nice in a bite). Spread the goat cheese mixture on 4 of the tortillas and top with the remaining 4 tortillas.
Lightly coat the skillet with cooking spray. Place 1 of the quesadillas at a time and cook until lightly browned. Turn and finish browning the second side. Repeat with the remaining quesadillas.
Slice quesadillas and serve sprinkled with crumbled Cotija cheese with salsa on the side for dipping.