the 8052 has a built in uart You could use that t uart to receive the ascii code,the programming is usually done by downloading your code serially from your pc using an in_built programming function and the 8052 and its derivatives have several parallel i/o ports which can be used to drive all kinds of things.
depending on what you need to switch on and off you might be better off using transistors rather than relays as relays are bulky and consume a lot of power,but basically you can do all you need with 8052 or a derivative,all you need to donow is work out which derivative is best,its all down to how many ports you need and which extra functions you need,some derivative are very expensive because they have lots of extras bolted on.Bewareof people getting you to use prosessors which are far too overspeced and overpriced for your needs..