What is the shariah ruling concerning converting local currency to stronger international currencies on the black market?

I am living in South Africa, where the US Dollar is approximately R12.00. The US dollar is considered as a strong currency and is accepted everywhere. However in South Africa, it is considered illegal to take out a foreign currency, accept with a VISA and ticket to a foreign destination. Assuming I want to perform Hajj in 2 years time. I do not know what the Riyal or Dollar will cost. Can I take out dollars on the black market and keep it until I have enough to go for Hajj? Barakallah Feek