Not that close, around 800m to either of Yuyuan Garden/East Nanjing road (the second has more lines/connections). It depends if you don't mind walking a bit - personally it was only an issue for me when getting to/from the airport (i.e. it crosses the comfortable walk with large bag limit) but it was fine for general sightseeing. The walk down East Nanjing road/the bund is very pleasant and is one of the "things to do" in Shanhai anyway to see shopping followed by views of the river and so on. Safety isn't going to be an issue either - especially not in these areas which are some of the busiest in the city.

However it depends on your view, if the subway is very important then you may wish to choose a hotel at people's square for example. As already mentioned - taxis are very cheap (i.e. a trip to the airport was only 250CNY, from the maglev it was about 50CNY), of course the subway is even cheaper. You can't expect the taxi drivers to speak/understand English so having directions written down is important.

Personally I'd not let the transport location influence your choice to stay there.