There's a few things which impact on low level reputation. The vanilla starter areas do not give any spill rep (Elwynn Forest, Dun Morogh, Durotar, Mulgore). Quests in any other area do give spill rep. Searching wowhead for 1-19 quests will give you problems because it will only show the first 200 results. Try using the zone listings within the quest section (eg.,
Database > Quests > Eastern Kingdoms > Elwynn Forest).
A 1-19 quest search limited to Alliance displays 822 quests. Currently I have cleared over 450 and most of Westfall, Dun Morogh, Loch Modan, Redridge Mountains, Duskwood and the smattering of other quests in less Alliance quest intensive zones. I expect there will be about 700 quests that can be completed, without accounting for seasonal quests.
Now I'll throw out some specious math which I used to guesstimate if Ambassador was possible at 19. This is educated guess work and I make no claim that it is totally accurate.
- 700 quests available
- average 250 rep per quest (some give 500, some give 10, I used 250 to help reflect spill rep)
- 700 * 250 = 175000 total rep gained
- 175000 / 5 = 35000 rep per city (there are 5 rep factions for Horde/Alliance)
- Friendly to Exalted takes 39000 rep
- Which leaves a rep gap of 4000, which I decided was good enough to take a chance on