Sorry for the very very late response. I visited Guangzhou the past two summers and in both cases ended up going to the Tianhe Sports Center for coaching. It was a fantastic experience and I can recommend that to players of any level. The coaches there are mostly former Guandong Provincial Team players (the boss being an ex-CNT champion), and very focused and friendly. My Mandarin is non-existent and they mostly don't speak nearly any English, but language barrier wasn't any issue - they would show me what they wanted me to do and mimic what I was ACTUALLY doing (mostly followed by loud - 'You - NO!' - and laughter on both sides). We would also use Baidu Translate (a counterpart of Google Translate) on our phones for more advanced conversational topics. My main coach was 21-22 years old and lots of fun. He charges 120 yuan per hour - which is about $20.
The Tianhe Sports Stadium is a pretty large complex and it may be a bit hard to identify the table tennis building. Here is the picture of the writing on the building, if you ask some local people, they will be able to send you in the right direction.
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This is my membership card from 2014 - the name of the place is on it as well - this may be easier to read.
You will find a general reception desk at the ground floor of the building. You can just pass by them and take the elevator to the third floor - there is another reception where you can fill out some simple paperwork, get the membership card, make a deposit, and look for a coach to work with. They have many tables on the third floor and there is a lot of training going on throughout the whole day. You will see a lot of little kids in the morning and more grown ups coming in the afternoon hours.
This is my main coach (ZKM)
and this is another coach who was helping sometimes - this one does speak English better than others.
If you don't have a coaching session scheduled, you can pay an hourly fee (I forgot how much exactly, but basically a few dollars), and play on the ground floor. I went there once to specifically play with my friend, and it was during lunch time when everybody else would disappear, so I am not sure if there is any challenge system or you just need to bring a buddy to play with. But there was a 'random' by-passer who observed us for a while and then asked for a match - so I guess they are pretty open to switching partners.
I was taking the APM line to the Linhexi (???) station (the last stop of the line) and it's about 7 minutes walk from the training center. On the way, you have to pass through a park which itself is quite tempting as it's full of outdoor tt tables. You will see a lot of grandparents stopping by to hit during the day, just put down their shopping bags and play in their fancy clothes. But in the evening, that place turns into a fierce battlefield with the younger generations coming to play after work - and I got some pretty good beating there ^^ I wouldn't normally think of playing outdoors but that area is not windy and the bounce of the tables is actually not bad - if you can put up with the merciless iron net. Cleaning the ball after it lends on the ground is also not a big issue - my rubbers were just fine, but the outdoor humidity is a bit of a problem for a player like me - the ball would often slip on the rubbers. So bring a big towel! If you're a hitter or a pips player, you won't even notice of course. The players in the park are pretty used to the conditions so be careful