"especially if you are a sci-fi nerd"
I watched it just now on your recommendation, on the grounds I am a sci-fi nerd, and you were right: the dialogue sucks butt. And in a way, I'm kind of surprised you weren't a little more upset by the movie, since a middle aged traveler dude loses his doggo!
But the plot, which is kind of "Wayward Pines" meets "The Time Machine," actually manages to meld these concepts into some fairly gripping, faintly original, sci-fi scenarios, and by cutting between various characters, it maintains intrigue from start to finish.
The special effects are actually terrific for the kind of low budget they would have had for this, and are cleverly reserved for only the specific limited moments they are necessary.
The lack of theme is a major drawback in a sci-fi movie, which genre is generally brilliant at casting a mirror over various aspects of humanity, but perhaps the generic characters are kind of too action-oriented and simply drawn to contemplate the finer aspects of all the dystopian worlds they are drawn into. Whether it be meeting ancient humans, future humans, relatives that age differently, strange fountains, catastrophic events, these characters all seem to behave like vacuous brain-dead teens (including the teens), spouting off nonsensical time-wasting dialogue, blowing all the opportunities for resonance. Still, the characters are functional, the action never stops, and the movie is consequently never boring.
All in all, this would make a terrific pilot for a cheap but action-filled teen show on a sci-fi channel, or a sci-fi show on a teen channel. And big picture, when you have very little money, and you come up with a picture as engaging as this, you've done good! :)