1. Your guess is correct. I haven't heard "vaya tiempo agradable" (Spain here), but probably it is fine in Central or South America. We do say "vaya día tan bueno" (what a nice day (weather). We use "vaya" in both derogatory and flattering ways:
"¡Vaya tío tan antipático!" ; "¡Vaya coche tiene Luis!"
2. In Spain people would probably say "en un segundo"; also, "palomitas al momento" (on the spot) Again, "al segundo" is much probably fine in other countries.
I hope this helps.