There are a couple of threads on Thorn Tree at the moment which use the term "gypsy taxi" to describe an unlicensed cab.
I haven't done much research but it seems that it is a reasonably common term in America and not considered offensive or politically incorrect.
I think I'd feel a bit uneasy about saying it though...

Gypsy cab is indeed the term of art ATM. One of 'em tried to nick me for over double the licensed fare a few days ago in Philadelphia, when I returned home from a trip. Its already high enough! No one seems to take offense at it. in part because there are relatively few Roma in the US, I suppose?
Ed

Considering that the vast majority of cab drivers in north america speak english as a second or third language so the term "Gypsy Cab" would likely be "foreign" to them.
Oh good lord. "Gypsy" (big 'G') may now be deemed an un-PC term for the Roma ethnicity, but gypsy (small 'g,' non-proper noun) also has a long history <blockquote>Quote
<hr>3. gypsy One inclined to a nomadic, unconventional way of life. 4. A person who moves from place to place as required for employment, especially: a. A part-time or temporary member of a college faculty. b. A member of the chorus line in a theater production.<hr></blockquote>
(American Heritage)
Furthermore, according to the OED, the usage of gypsy to mean "independent or unlicensed operator" of a vehicle dates from at least the 1950's in the US. I accept that we can no longer call Gypsies themselves "Gypsies" (on the slightly strange grounds that it isn't what they call themselves--by which logic we should also call Spaniards "Españoles," Russians "Russkie" and Georgians "Kartvelebi," etc., when speaking in English) but let's not get totally ridiculous.

Furthermore, according to the OED, the usage of gypsy to mean "independent or unlicensed operator" of a vehicle dates from at least the 1950's in the US. I accept that we can no longer call Gypsies themselves "Gypsies" (on the slightly strange grounds that it isn't what they call themselves--by which logic we should also call Spaniards "Españoles," Russians "Russkie" and Georgians "Kartvelebi," etc., when speaking in English) but let's not get totally ridiculous.
Except that there is nothing like the negative associations connected to "Spaniards," "Russians" and "Georgians" that there is to the word "gypsy." And the truth is that many Roma do call themselves "Gypsies" and no credible source is actually claiming that the primary reason that "Rom" or "Roma" should be used is that that's what they call themselves. The reason is simply that it's probably the most widely known term for them without a long history of negative associations; it happens to have the added value of being used by the people themselves in many cases.
Yes, "gypsy" has a long history of being used to describe things not directly related to the actual people, but that doesn't make it less of an offensive term. Not terribly long ago, it was considered fine to use the term "jew" to describe what might be described loosely as a negative bargaining action. (As in, "He tried to jew down the price.") The person in question might not have been a Jew, but the negative association exists nonetheless, and that's why the term "jew" in that sense is rightly considered offensive. The same is true of "gypsy" in many cases, which is why educated, sensitive and polite people would not use it in that fashion.
Most Americans know next to nothing about the Roma, and aren't aware of the fact that even within EU states in the past few years there have been (to cite some examples) forced expulsions of Roma from their native countries, forced sterilization of Rom women for no medical reason, vehemently anti-Rom public statements by governmental leaders, the denial of basic human rights and so on. So it's not surprising that they rather idiotically continue to use a word which offends many Rom people.
Yes, by all means. While we're at it, let's also go back and change the Broadway show Gypsy into Lascivious Showperson!, the popular Spanish band into The Roma-influenced Kings, and Keats's poem into "The Scholar-Wandering-Person-of-Limited-Means."
The ironic thing is that "idiotic" Americans, with their romantic notions, probably esteem Gypsy culture a great deal more than the majority of Europeans do. Those that have actually lived in countries where they are a ubiquitous public nuisance (myself included, for 8 years) tend to take a dimmer view...and to forthrightly acknowledge that, whatever their virtues, at least some of those "negative associations" are not entirely unmerited. In any event, I will continue to use what (once the PC SWAT team really gets up to speed) is probably destined to be known as "the g-word."