As someone intensely interested in language, I do not accept Sprachgefühl in a general monolingual English context. If I ran across it in writing, I would consider the writer a preening, pedantic show-off.
Even in a high-falutin' language-oriented context (such as William Safire's "On Language" column in the New York Times) I would find this word unacceptable--except for a column where "Sprachgefühl" itself were the topoic under discussion, in which case it would be defined in context.
A bilingual forum such as Leo is a clear exception--I *would* accept it here, because I expect everyone to have some level of bilingual competence.
Whether something is acceptable or not is, of course, a judgment call, and things may be different in the UK--my competence is in AE, and I'm stating my opinion only. To indicate my bias, I tend to be pretty liberal about what to accept, and I would unhesitatingly accept Schadenfreude, Wanderlust, Blitzkrieg, Fingerfehler and many others, but sorry--no Sprachgefühl (yet).