Where are you driving to Dallas from? That might help us help you.
Yes, I agree, around Fair Park it is not a great neighborhood.
Mill Creek RV Resort in Canton, TX is about an hour east of Dallas depending on traffic. It is a very nice park.
Mill Creek RV Resort is a great place... but it is about an hour east of the Dallas City Limit, but more like 1.75 to 2 hours to the State Fair, depending on Dallas traffic.
There is also
Bluebonnet Ridge on I-20 near Terrell, TX east of Dallas, but again, this is about an hour from the State Fair.
We haven't stayed at Cedar Creek State Park, but scoped it out for a future visit. If you are good with backing, it looks like a nice park, with lots of sites. A little note about Texas State Parks... You can make a reservation, but they do not reserve you a specific site... it is first come, first served the day you arrive... you pick your own site. And hopefully you'll find one you like.
Erika