Two interesting questions. Let's examine them. First, how many cross here to get one? I'm sure I couldn't say. But if this is truly a problem. Then let's switch the country to Guatemala. Certainly, there aren't too many people with enough money to hop a plane up to L.A. to get an abortion there.
But your second question is really depressing isn't it? I seems you are saying its possible there really isn't that big of a difference between abortion rates in the U.S. and Mexico, its just that since its illegal in Mexico they aren't reported.
This, of course, is precisely Planned Parenthood's line. They argue legalization of abortion simply provides 'safe' abortions for those who would get abortions anyway. Now, I have read articles which, to my mind, prove this is false and that, in fact, legalization of abortion causes a huge upswing in abortion. Indeed, some scientists speculate the epedimic of breast cancer in this country is due precisely to the increase in abortion after abortion's legalization. Thus, while I can't answer your question with any degree of precision, I would say that -unless one wants to accept Planned Parenthood's and the abortion industry's argument- the abortion rate is lower in those nations in which its illegal.
Of course, viewed on another level. Both questions are really irrelevant, aren't they? The laws passed by a society are an expression of that society's views on important issues. Thus, even if the rates were exactly the same, it would still seem to me to be an interesting question as to why the society in which Bibles are plentiful sees abortion as a constitutional right while the society in which Bibles are less plentiful at least sees it SHOULD recieve some form of condemnation?