The quick answer is no, it’s not too late. The manufacturers of central vacuum systems have become very creative on where they run there tubing. They work around the house through the attic, basement and garage, and then they can drop the tubing down behind the interior walls from the attic or push it up from the basement. In some instances they may use a cold air return to get the tubing to the proper location. When your central vacuum system is installed you will be amazed at where they can get the tubing to without any visible signs of damage.
There is a higher cost to getting a central vacuum system installed into a home that is already built as opposed to installing the system as the house is being built. For many people the cost of a central vacuum system is worth the additional cost this cost however is many times the cost of a regular vacuum cleaner. If you decide on the central vacuum system I recommend that you get a professional to install your system, you should also get at least three quotes for the job.