How do I avoid double taxation between RSA and the USA?

I just invested in a Global Property index fund held under a tax-free savings account. I believe this is exempted from SARS 15% dividends tax. The IRS tax rate for foreign investment goes as high as 30%! Is there a possible chance that I may be taxed twice, dividends tax and then capital gains tax, when I sell and bring over the amount back in South Africa?

Is the tax-free savings account sanctioned as one by SARS or is it a foreign account?

The tax-free savings account is from South Africa. Grindrod's Global Property Income Feeder Fund.

Grindrod should negotiate any taxes with the USA and they seem to be offering this as an after tax product. You would need to speak with them about this however.