Hungary. Esperanto is available to students in school, so there is a slightly higher density of Esperanto speakers than in most places.
China. It's not massively popular, but there have been waves of Esperanto fads, enough so that there are quite a few speakers there (perhaps 10,000 active and 400,000 with some skill in Esperanto). There have been communist officials who advocated replacing Chinese with Esperanto, but they didn't succeed. You can read official Chinese news in Esperanto, however: China Interreta Informa Centro-esperanto.china.org.cn. China still has the best-attended Esperanto gatherings.