Final answer:
The italicized prepositional phrase 'Before we went to my hometown park' functions as an adverb, providing information about the timing of the action.
Step-by-step explanation:
The sentence provided, "Before we went to my hometown park," contains a prepositional phrase that begins with 'Before.' In this case, the prepositional phrase functions as an adverb because it modifies a verb by giving us information about the timing of the action. It answers the question 'when did we go to the park?' Therefore, given the options, the correct identification of the italicized prepositional phrase is as an adverb.