Racing Lines (Australian Mag) and Radio Controlled Car Racer (British mag) are the best two IMO. A fair amount of on road content and a lot of race results and reports from all around the country's in question.
I also read a couple of the US based mags, but, to be honest, they are not even in the same league as these two. US mags have a greater proportion of advertising and less over all depth and originality in product reviews. I do not remember the last time a reviewer found fault with anything in a US mag.