Thats a tough one. The properties of the venturi siphon physically "should" work. Even with the change of elevation, the suction that is produced in the python from the sink is not going to be elivated due to the pressure it will take to pull the water through. Basically there is a certain force your venturi siphon is going to have to create in order to over come the gravitational force to pull the water up the hose.
In my eyes, assuming you have a descent amout of water pressure that isn't going to allow the pressue building in the hose to disipate, over time enough pressure will be built to pull the water through. This is the only problem... the cheap water bed type peices they put on the end of the python don't hold this pressure well, but this is the only thing im not sure aobut. The amount of time it takes is the amount of time it takes to build that pressure.
The idea that once the water gets to the end of the hose it should be fine is wrong. It isn't a traditional siphon principle that the flowing water is what keeps pulling, its the venturi's ability to produce a pulling force in the hose by using pressure provided by the sink. With that being said even if you had the water in the hose at the sink, and turned on the python, it wouldn't start pulling water through until you build up the pressure required to continue pulling through the assembly.
In my eyes, if you are patient enough, and your sink has enough water pressure to allow the siphon to hold the pressure in the hose, and assuming that the venturi can keep the pressure its building, it should be fine.
Give it a try and if it doesn't work, take it back, thats why stores have return policies, just make sure you check first.
