Sorry .. I realise that last posting wasn't particularly helpful! I think you're right in picking up on 'hispanic' as a word where there's a certain amount of variation in use of a / an. But I don't think it's necessarily because it's a loan word or a neologism - I think people would generally put an 'a' before words like 'Hottentot' for instance, which are even less familiar. I'm not really sure about this, but I think there could be two or three factors leading to some speakers at least putting an 'an' before 'Hispanic'.

I think phonetically, the sound 'h' is pretty un-consonant-like and suffers the indignity of frequent elision in any case. But this is particularly the case when it's followed up with the short 'i' sound and maybe then the sibilant 's' .. this is just speculation really .. but the word 'history' went through quite a long period when it was considered correct to use an 'an' before it .. eg in Jane Austen's usage (I think) - ok, this might also reflect an older pronunciation of the word - influenced by French 'histoire' - so I'm not sure if that's a particularly strong argument. But I think that other 'his' words still tend to swing both ways. In the last example of my previous posting, I used 'an hysterical ...' which doesn't really sound as wrong as some of the other examples I included .. so I think the main reason is a phonetic one.

On top of this, in the case of 'hispanic' there could be grammatical and usage influences .. because it's used more as an adjective than a noun, that might cause a bit more uncertainty about the 'a / an' thing and because I guess that a lot of people who use the word may themselves come from a hispanic background, there might be a bit of language transfer going on from Spanish or Portuguese.

If you're interested in having a look at some written examples, there are several concordances online .. an easy one to use, I've found, is:http://www.collins.co.uk/Corpus/CorpusSearch.aspx
The instances of 'a Hispanic' and 'an Hispanic' there are roughly equal, by the way. I also had a look in the British National Corpus and what really struck me there was the strong association of the adjective 'hispanic' with discourse about crime (as with the word 'Caucasian') and politics - the expression 'black or Hispanic' crops up again and again in the corpus data...