Actually, all you need is for the Spanish expulsion of the Jews to be delayed by a few years (logistical reasons, perhaps; an attempt to make sure that the expulsion is thorough and that the victims are properly looted). Once Columbus comes back with word of lands to the West, that would be seen as a convenient solution for dealing with the Jews and the Moors: send them west to establish colonies and then squeeze them for money. It also helps deal with the key problem of most European colonial efforts; namely, that finding willing colonists was extremely difficult.
Of course, a Jewish/Muslim Caribbean and Brazil (once the Portugese join in on the expulsions) would be interesting, to say the least. Especially since they'd probably still have a body of religiously acceptable Spaniards to keep them under control and sending wealth back home, rather than taking the chance to rebel...
This is a very interesting idea, and, if it had been implemented, it might have let to a more diverse, tolerant, productive and interesting Spanish America.
However, it would have required a significant change of the Spanish King's policy. In 1493 there were still Moors in Spain (forced conversion of Granada's Muslims only occured around 1500 IIRC), and a lot of forcely converted Jews who secretly practiced Judaism.
The Spanish Kings could have send them to America if they had wanted to, but they were entirely against the idea. They didn't allow anyone who wasn't an "Old Christian" (somebody whose ancestors had been Christians for more than 200 years) to go to the New World.
The ideological justification of colonization was the conversion of Amerindians. They feared Jews and Moors could gave natives wrong ideas about religion. That's the reason why, a few decades later, they extended the prohibition to travel to the New Words to "heretics" (Protestants).
The other reason was that they probably weren't sure of how loyal would Jews, Moors or Protestants be.
Of course, some Jews managed to came in the colonial era. There are a few comunities in Central America who have been practicing a form of secret Judaism since the XVI century. In the recent years some of these have began to practize it openly again, re-converting to their ancestors faith.
Other (converted) Jews went to Brazil, as Portugal was less serios in terms of controling who left to the New World. Some of these later went to Spanish colonies such as Buenos Aires.
Others probably managed to pass Spanish controls and immigrate.
But they where always very few and isolated. To get more, you'd need a real change in the Spanish King's minds.