It seems to me that the headline question here—"What preposition is used after 'enthusiastic': 'for' or 'about'?"—differs fundamentally from the body text question, which appears to be "Which works better—'get enthusiastic and hopeful for' or 'get enthusiastic and hopeful about'?"
The obvious difference between the two questions is that the headline question asks whether to use for or about after the word enthusiastic, while the body text question asks about whether to use for or about after the phrase "enthusiastic and hopeful." Because readers are far more likely to run afoul of the headline question than of the body text question, my answer addresses the former.
In my view, uncertainty about whether to choose "enthusiastic for" or "enthusiastic about" is due to the influence of a separate pair of phrases—"enthusiasm for" and enthusiasm about." The problem is that "for" is the more common preposition in one of the phrase pairs and "about" is in the other.
Here is an Ngram chart tracking the relative frequency of the phrases "enthusiastic for" (blue line) versus "enthusiastic about" (red line) versus "enthusiasm for" (green line) versus "enthusiasm about" (yellow line) for the period 1800–2005:
Year in and year out for the past century, as the chart illustrates, "enthusiastic about" has been considerably more common in published writing than "enthusiastic for"; but during the same period, "enthusiasm for" has been vastly more common than "enthusiasm about." That is, idiomatically—and notwithstanding the seemingly contrary directions their preferences take—English writers (and presumably English speakers) show an overwhelming preference for "enthusiastic about" and "enthusiasm for."
So (removing "and hopeful" from the example sentence in order to focus on which preposition works best with enthusiastic/enthusiasm), we have two idiomatically favored pairings, either of which sounds perfectly natural:
...might present more difficulty to get[ting] enthusiastic about religious and mystic issues.
...might present more difficulty to feel[ing] enthusiasm for religious and mystic issues.