To whom is Lot speaking here, bearing in mind that he is pleading for his life?
Targum Onkelus and Rashi: The last word in the Pasuk is Kodesh, as Lot was pleading directly with HaSh-m to have pity on him and spare Tzo'ar.
Targum Yonasan: He is actually asking the angel to wait until he Davens to HaSh-m. 1
Riva: The first request was to the angels, that they not force him to go to the mountain. The next to request was to HaSh-m, to keep him alive.
It seems that the angel granted him his request, and verses 19:19-20 contain the wording of Lot's Tefilah to HaSh-m.
QUESTIONS ON RASHI
Rashi writes: "Onkelus translates ["Al Na, HaSh-m"] as, 'Please, now (b'Va'u ke'An), HaSh-m.'" Targum seems to skip over the word "Al" (do not); and he translates the word "Na" twice (as both "please" and "now")!