The recent Southern fiction issue of Oxford American had a piece about Donald Barthleme that discussed in some detail his story "City of Churches".
As a freshman at the University of Alabama in 1979, I was put in the advanced English class which as far as I could tell (or remember) meant that there was more focus on literature than continually writing papers. When we read Sartre's story "The Wall" one student started discussing how this tied in to existentialism as if we all knew what was what but as a small-town kid from south Alabama, unlike this Birmingham guy, I'd never heard about any of that. (And if you're not a Southerner you likely won't realize that north and south Alabama are quite different.) Growing up I read constantly, didn't watch much TV and not many movies, and the reading was nearly all SF/fantasy with bits of parallel lit (Doc Savage pulps, a few mysteries here and there, some of the more ghost-story-looking romances like Victoria Holt, military histories). But I didn't read Sartre or for that matter almost any of the standard canon, not even in school.
So when the class came to read "City of Churches" I ended up in an oddly reversed situation. The story is about a woman who visits a city where all the buildings are churches. The class went nuts and had the hardest time with this but for me, who'd spent years reading books with radically different worlds or even laws of physics and where actually specifying the changes in detail was considered weak writing, for me this story was no problem. In fact I loved it in a way I didn't the Sartre. (Though today I have resisted re-reading Barthleme because of a feeling that I'll find him far less interesting than I did in my 20s. And I've still read almost no more Sartre.)
So reading SF/Fantasy made me more open to postmodernist writing? Maybe, it certainly creates a greater willingness to tolerate differences, at least for a while. Still I suspect this is more related to whatever quirk made me instantly like free jazz, musique concrete and structuralist film (not to mention other writers from Pound to Borges to Pynchon). After all most SF/Fantasy readers can be quite dismissive of experimentation of any kind.