No problem just make sure caps are on and they are secured , just stand the acetylene bottle upright for a while before you use it
Tom

yes remeber the caps and lay the caps facting the cab of the truck just in case something happens and a cap and valve get knocked off the shoot thru the tail gate and not the cab of the truck

Best practice is to transport cylinders upright and secured.

HNirider,

When we came to AZ from OR a few years ago I brought about 6 tanks with me.  All were owner tanks.  No name on the ring around the neck.  It was no problem at all to have my new local supply take them and fill them.  They rotated them so I did not necessarily get the same ones back.  All mine had good dates for having been recently tested so there were no issues there.

I recently changed suppliers here in AZ and was told the same thing.  As long as they are current and are owner tanks with no other company name on them and only identified with stickers as to who had supplied them and what the mixture was, it is an easy switch to a different supplier regardless of state lines.

Also, as witnessed by the picture by Northweldor (Great Pic), it is not the properly recommended nor safest method of transportation to lay the tanks down. 
  *According to AISC 'General Safety Rules for Structural Steel Fabricators', 9.16: "Cylinders should be stored, transported and used in an upright position."  This is especially true of Acetylene because of the way it is generated within the tank in the first place.
  *ANSI Z49.1 'Safety in Welding, Cutting, and Allied Processes' differs to the various Departments of Transportation.  Check your states you will be travelling through to be safe.  They do stress the safely securing of cylinders to be transported.
  *OSHA Subpart J; 1926.350  in several clauses states, 'firmly secured', 'secured in vertical position' when transported by powered vehicles, etc.
  *AWS 'Independent Shop's Guide to Welding Safety and Health' gives several good points but as to vehicular transport goes to DOT and the Compressed Gas Association publication P-1.  Around the shop- safely secured in the vertical position even for transport.

Whatever you do,  SECURE THEM VERY WELL.  Many things can go wrong. 
2) Check with your DOT for safety rules.
3) If at all possible, transport in the vertical position.  It is safest. 

It will be said, "I've done it this way for years.  Never had a problem."  It only takes once.  And there have been many documented accidents through the years from transporting bottles improperly.  Acetylene is very unstable.  Treat it with great respect.  If transported horizontal, give it a lot of time vertical before using.  The longer the better. (And it is still hard on the tanks. They get eaten out from the inside when the chemicals are allowed to move improperly and no one knows until it blows.)

Just my two tin pennies worth.  Be SAFE.  Good luck.

Have a Great Day,  Brent