"Please arrive early!"
Translation:Bonvolu alveni frue!
It is a command -- see the "u" at the end of "Bonvolu"?
If you want to have "alveni" in the command form instead of "bonvoli", you can use "bonvole", the adverb form:
Bonvole alvenu frue!
Both options ("bonvolu fari X" and "bonvole faru X", with any verb you like instead of far-) are common.
I made the same mistake, but it's quite logical
Bonvolu is the infinitive of bonvoli. So technically it means something like "do me the favour" or "be so kind". We can also turn it into the adverb bonvole = please, but that doesn't want to stand on its own in Esperanto. As mizinamo already explained, the two correct options are as follows:
- Bonvolu alveni = Do me the favour of coming = Be so kind as to come
- Bonvole alvenu = Please come
If we just join the two imperatives, we get something similar, but quite different in spirit:
- Bonvolu, alvenu = Do me the favour, come = Be so kind, come
I think the main difference to the previous two versions is that this is not the most idiomatic way of saying it and therefore it tends to be used only in special situations, to express a special nuance.