Rashi (Genesis 19:1, "BaErev") asks rhetorically, וכי כל כך שהו המלאכים מחברון לסדום , implying that it's close from Chevron to Sedom. But if we assume that Sedom was located where the current Dead Sea is (or thereabouts), it's a distance of some 20 miles, so it would take from morning until evening to walk there. If they visited Avraham "Kechom hayom" that implies sometime between 10-2, so how can we say that's tarrying?
Artscroll Rashi Breishis page 192 brings two explanations. Gur Aryeh says that Biblical Sodom was not at the same location as current-day Sodom. Bereishis Rabbah 50:1 says that the angels are not limited by the constraints of men and could of traveled from Hebron to Sodom instantly.