real world colonization

All this talk about settling new worlds has one major
problem: Is there a place to settle?  IF (make that a
very very big IF) there is another "earth-like" world in 
another star system (oops, make that 2 problems: 
is FTL viable?) who says that its environment is totally 
safe for humans to walk unprotected.  How long would it
take to "terraform" that world?  Can it be done or
would the native life be hostile and hard to eliminate
or replace by Earth life?  Can Earth plant-life live
under a different sun?	We have a hard time surviving
in a semi-hostile world here on Earth: underwater.
Where are all those underwater cities envisioned by
sf authors of many years ago?  There's one underwater
"hotel" here off the Florida keys, it has one room.
I haven't heard of its occupancy rate.
Mars is going to be difficult to settle, and not within
100 years, especially on how little we spend on
space technology.  Space travel is hard and dangerous,
it's not like making a boat or wagon out of wood and
going somewhere.

Of course, man was only flying in lighter-than-aircraft
100 years ago.	But, FTL may not be possible at all.

Fiction is another matter, in which case anything can
be made up for reasons for space expansion.

Glen