I'm relating my experience with 8ta, based on a sim I received and tested (a week ago). They may state that it's only 2g, but that's not what I get. And it's definitely roaming - there is a unique roaming symbol - a triangle - that is displayed.
As for the 8ta towers, I guess that goes back to the original post - where are they?
EDIT:
I didn't purchase the sim - it was free 
Hi TheMightyP
If you ever ride past St Albans (Past Greenbushes on the Cape Road) bring that 8ta Sim with you and stop by the Exchange(Right next to the St Albans Prison), you will notice a large Tower. That Tower belongs to Telkom (8ta) it's their 3G Tower for the surrounding area. If you pop your 8ta Sim into your phone/laptop etc and do a check as to what 3G signals you can pick up in that area, you will get Vodacom,Cell C and 8ta.
There is no 3G MTN any where in the surrounding areas 
If you try to run a speedtest in that area with
that specific 8ta Sim card you have, two things will happen:
1. You will not get 3G speeds, due to there not been any 3G MTN of course. You will be forced to MTN 2G(Edge) speeds.
2. I personally don't think you will pick up the 8ta Tower as well, despite you been a few meters away from it. My opinion (this is only my opinion mind you) for the reason for you not picking up any 8ta Towers is because you have a normal Roaming 8ta Prepaid Sim. Those Sim's are basically on roaming 99% of the time and will never connect to a 8ta Tower, even if your sitting on top of one
If I'm right,
NO 2 is the reason why you think there is no 8ta Towers in Port Elizabeth, you need to get one of these Promo 8ta Sim Cards (2Gig+1Gig one is simpler). Once you have the new Sim,
YOU WILL pick up a 8ta Tower in Walmer. The roaming symbol which you pick up now, will vanish.
That link to my speedtest results(10Gig 8ta ONLY) which MickeyD posted, come from that St Albans area where there is NO 3G MTN.
There is one thing which stumps me as to why you are getting 3G speeds if it's a normal 8ta Prepaid Sim. As MickeyD and OMB mentioned you should be restricted to 2G speeds. I'm going to test my old Roaming 8ta Sim Card at work (3G MTN is available) tomorrow and see what's going on.
