>If you could instantly reach a 'speed' above the speed of light you would be OK. If you could fold space (as mentioned by OP) you would be OK.
If you could twist into another dimension (string theory gives 10 to play with) you would be OK.
>It may be science fiction today. But so was the heliocentric universe, so was ether-less transmission of light, so was oxygen, ... need I go on?
Oy, logic. The argument that "scientists were wrong about x, and thus they are probably or may be wrong about y" is specious at best. In fact, you can use it to claim anything you want. Scientists were wrong about the "earth-centered" theory about the universe; therefore, they may be wrong about my sincere _belief_ that the government planted a radio transmitter in everybody's head at birth.
The fact is, we have to/ ought to go with what we can prove, and save the speculations for the science-fiction writers. There are a world of people trying to convince us to "believe" in their suppositions. I "believe" in my family and my university. For everything else, give me hard empirical evidence.
And besides, the earth-centered theory fell because there were problems with it. It did not accurately predict the positions of the planets. Astronomers toyed with various weird variations of it to get proper positions, and none of them worked. The principles that make near-light velocities prohibitive are well tested and have developed no such anomalies. They have stood up to the most rigorous experimentation. As above, you've got to go with what you can prove, rather than what you'd like to believe.
As for the other speculations, "folding space" sounds so fancy and scientific, but it merely refers to Einstein's notion that gravity is simply the bending of spacetime around a massive object: the more mass, the more bending, the more gravity.
Thus, when physicists speculate about "folding space," they are talking about folding very tiny sections of spacetime. In fact, in a sense you are folding the spacetime around you as you sit in front of the computer as your body applies its gravity to the surrounding space.
To fold the space between here and a star, say, 1,000 light years away would take energies and masses that approach the total mass/ energy output of the entire Milky-Way galaxy of 300 billion stars.
The 26 dimensions implied by string theory are already present in spacetime. They are just, as one writer put it, "very, very small, too small for us to detect." You don't "twist into them" any more than you twist into your height, width, breadth, or duration (time). You exist in them already. It's like saying. "If I could just be taller, I could reach out and touch the star Alpha Cygni."
Saying otherwise is like saying, "What if I could create a round square?" It's fun to speculate and play games with the language (That's what science fiction is all about. I personally subscribe to the three major American mags.) But it's just that -- fiction.
As for instantly reaching the velocity of light without accelerating to it, well, that's just a meaningless phrase. A body at rest tends to stay at rest unless acted upon by an outside force. (And don't tell me that Newton could have been wrong. His equations have stood the test of time.) You have to apply energy (a LOT of energy) and accelerate to get to a specific velocity like .5C.
We've got to go with what we know. Thinking about the threat of aliens is simply a fun pastime. Personally, I'd rather think about solving the more immediate problems that have mounds of empirical data to support their existence.
Shoot, folks. Speculate away. Have fun. I'm done. I just killed too much time, and I've got a bunch of 4th graders coming to the Observatory today.