Javier BF wrote:

> I'm a native speaker of Castilian Spanish myself,
> thus what I'm telling you is not hearsay but personal
> experience. English "yet" sounds like what in Spanish
> orthography I would spell "hiet" (like in "hierro"),
> not "yet" (like in "yerro"). Personally, I easily
> notice when a foreigner is mispronouncing Spanish y
> as [j] and if I were to imitate the average foreign
> accent of English speakers, I would say "hiou hia
> hiamey" instead of "yo ya llam". But many other
> native speakers (most in fact) aren't _aware_ that
> a certain speech is sounding foreign because of the
> mispronounciation of y as [j] and will simply say
> that "It just sounds foreign, I can't tell you why".

There are a few another clues (the kind of clues that makes a foreing sound
foreign while untrained Spanish speaking natives cannot know why), like
pronouncing every voiced stop /b/, /d/ and /g/ as stops [b], [d], and [g]
even in intervocalic positions, or like aspirating the voiceless stops (i.e.
[t_h] for /t/).  The pronunciation /r/ and /rr/, the quality of the vowels,

If you know what to look, you can even recognize the substract language of
the foreigner.

And, of course, I can hear the difference between "hierro" [jerro] and
"yerro" [j\erro], or between "hierba" and "yerba", as I am sure most Spanish
speakers in the Americas can.  Misspronunciation is common, though, but
usually refered as a vulgarism.

-- Carlos Th