Driving License

I am thinking to buy a minibus/van and do little camper conversion.
From what I find on internet I like Hyundai Grace DLX Grand Saloon.
It usually has 15 seats, I only want to leave 4 in.
My doubt is will I be able to use my current international driving license to drive this minivan around?
In my country I have a B category driving license allowing me to drive a car with up to 3500 Kg weight and 8 passenger seats (excluding driver). So to drive this van in my country, even I take 11 seats out, I would still need to upgrade my driving license.
I have heard in CR, first 3 months I should use my international DL and after that I can convert the international DL to local.
For the minivan, do I need to upgrade my license before entering CR? I do not like this idea as I am not yet sure what car I get...
If I arrive with my current license will I need to upgrade it in CR and is it doable with no Spanish?
Thank you.

You cannot obtain a Costa Rica driver's license until you have become a legal resident of Costa Rica and are carrying your cedula.  You are able to drive with your foreign driver's license for 90 days after the date stamped in your passport of when you last entered Costa Rica.  Many people who are waiting on their residency make 90 day border runs in order to legally drive in Costa Rica.  We made four runs to Nicaragua while waiting for residency approval.

Thanks for answer. I will have the resident status that comes with a work visa.

Does anyone know what driving permit is needed for 15 seat minibus i.e. Hyundai Grace.
What I know in UK for an instance all you need is normal car driving license + 2 years of experience + not driving for money (weird one) - http://www.drivesafe.org.uk/Minibus-Dri … tion-.aspx
I want to make sure I do not need to do any driving license upgrade before arrival.

Your home license will be valid, but it must correspond with the vehicle licensing requirements.
It may be hard to find accessories for doing a conversion...