My girlfriend (Kenyan) says people normally just say "vipi?".
Just some extra info.
In Tanzania, both mambo vp and just vp are very normal.
How about just mambo? That's what I heard the most in Western Kenya
As far as I understand Western Kenyan Swahili is very slangy
I think all of the suggestions work. But when travelling in east africa it is good to keep in mibd that tanzanian swahili usually us more formal and gramatically correct than Kenyan kiswahili.
This one is colloquial and less formal, right?
Think so (https://en.wiktionary.org/wiki/mambo#Swahili)
plural of jambo
(colloquial) how are you?
'How's the going?' wouldn't be heard in England, but is common in Nai. I submit this was an excellent translataion, even if marked wrong :-)