Morthond extends all the way to that spur of the White Mountains. Several hundred rangers seems probable when considering that it covers both North and South Ithilien, Emyn Arden, and the fords of the Poros. Gondor had several watchposts in Harondor. Before the Battle of Osgiliath I mean before the War of the Ring, so before the scene in the film where they cross the Anduin, so they'd still have a couple thousand troops there. It's pretty realistic, given that Minas Tirith's troops are spread between itself, Osgiliath, and Ithilien. Yeah I should add a thousand to Belfalas, and another 2,000 to Dor-en-Emil. Actually, Morthond Vale is a sub-province of Lamedon, so we'll just delete Lamedon and put 5,000 for Lamedon, also take into consideration that there IS a city - a fortress, in fact: Erech. Tolfalas' population status is unknown. It is possible that they established outposts against Umbar and ports for those who don't want to all the way up to Pelargir and Harlond. It wouldn't mean 20,000, because that would imply 15,000 women, children, infirm, elderly, and several cowards vs. 5,000 men, which I doubt.