Where's the best place to park if you want to go the Conference Center, Temple Square and City Creek Mall?

There is street parking everywhere (metered nearby, free within a couple blocks) as well as huge parking garages under the conference center and City Creek. If you plan to attend the temple, park at the conference center and get a validation token at the recommend desk.

As Jenjen said. ☝️

If you park in the underground parking space and get a ticket at the Temple you can park for free.