Von Neuman machines are even less likely considering they would still have to remain fully functional over a truly geologic timescale in order to be in any way functional. If you had technology that robust, it wouldn't need to be self-replicating because it would basically last forever. It's a Crazy Eddie concept that otherwise serves no practical purpose.
It's mundanely obvious that interstellar travel is perfectly feasible for an unmanned probe that can expect to be discovered intact after a billion years or so by an alien race that didn't exist when it was launched. Travel or transport LIVING BEINGS just isn't going to happen, though, without a space fold or something similar. Or -- as Gary mentioned -- if a civilization evolved near the galactic core or in a dense cluster of stars, in which case interstellar travel only takes slightly longer than interplanetary travel.
Still. greater numbers means two things: You still have more machines out there after falling prey to attrition through disaster, wear and tear, etc. Also more machines means covering the distance at sub-light more quickly, spreading like a virus.
First of all, they wouldn't spread more quickly
at all. They would spread more EVENLY, but still take millions of years to do it.
Second of all, even a virus requires a viable host to reproduce itself, as to Von Neuman machines require a source of plentiful and accessible resources to use for self-replication. Interstellar space has no such resources, and even if it did, they are hardly in a form that self-replicating machines would find easily accessible.
Lastly, the concept of the Von Nueman machine is one that is only theoretically viable on a relatively small scale -- say, mining a moon or an asteroid or something. Using them to spread your influence across an entire galaxy is a bit like trying to build a suspension bridge out of legos and superglue: an amusing hobby, but hardly practical.
Yes you can expect organic beings to make it across interstellar distances, but more realistically by the methods i named. Its perfectly feasible to recreate humans once we meet up with our robotic explorers.
You can say that if and when we have discovered a way to keep frozen embryos viable over a span of half a million years.