Your translation is very close and only requires a few tweaks.
For context, Cicero introduces this passage a little earlier: he is talking about the five stellae errantes ("wandering stars"), which he sees as a misnomer:
Maxume vero sunt admirabiles motus earum quinque stellarum quae falso vocantur errantes; nihil enim errat quod in omni aeternitate conservat progressus et regressus reliquosque motus constantis et ratos.
Translation:
But the most admirable of all are the motions of those five stars which are incorrectly called "wandering"; for indeed, nothing "wanders" which preserves for all eternity [the same] constant and calculated advances, retreats, and other motions.
Once we realize this, the passage becomes fairly clear: the only tricky part is the first sentence, which changes the word order a bit. If it helps, the following word arrangement might seem more natural to your ears:
Stella Veneris est infima quinque errantium et proxuma terrae...
An almost literal translation, with the relative clause split in two to avoid awkward syntax:
The lowest of the five wandering [stars] and the closest to earth is the star of Venus, which is called "Phosphorus" in Greek and "Lucifer" in Latin, when it precedes the sun, but "Hesperos" when it follows after.
As pointed out by Ben Kovitz, Cicero is not saying that "Hesperos" is only a Latin name. This is clear because of the chiasma of "Phosphoros Graece, Latine Lucifer," which creates a single unit of comparison that is qualified by "cum antegreditur." This division is also clear from the fact that "Lucifer" is a literal translation of "Phosphoros" (= "light bearer").
