Should I call him to let him know I am coming in town?

Well, you have a month to clear this up - enough time. You need to first discover why he "suddenly stopped calling". Surely you must know something about why. That is key. If you find that he stopped because he is no longer interested/dating another/hates you/etc. , then you definitely do not want to tell him you are coming to town. Because you don't want him to be able to prepare for your "visit" when you go to burn down his house/slash his tires/eviscerate his dog/etc. (Just kidding about the dog part. ) No, all that could mean jail time and nobody likes jail time (unless you have kids and just "need a break"). BUT, if you find out that he is too busy with work/mom's been sick/telephone disconnected/un-employed/in rehab/etc. Then you definitely need to let him know you are coming so he CAN prepare for your visit. He will need to clean up his place, clear his calendar, buy some new food (and underwear), wash his car and trim his nose hairs.

So, basically, you need to call him. Then, you will know where you stand (and if he lives or dies). Good luck. :)