All puppies are sweet and cute; yours will be no different. Chihuahuas are sweet and cute as well, and your Chihuahua will be super friendly to you. Chihuahuas are unique in that they fall in love quickly with their masters but don't often have any interest in meeting other people or other dogs.
Chihuahuas are very comfortable within their own spaces, so to teach your Chihuahua to be friendly you need to expand his personal space. Having a friendly Chihuahua means your dog won't give off the scary bark every time your doorbell rings or a guest walks in the house. A friendly Chihuahua won't growl at your guests as they reach over to pet him or pick him up. A friendly Chihuahua sits in your lap and allows others to be near you. A Chihuahua, if not taught to be friendly to other people will come across as aggressive and possibly even mean. This is not what their personality is; they are just built to be the only dog in your universe and need to be trained that your universe doesn't always revolve around them.
The trick to training your Chihuahua to be friendly from the start is to get him social as early as possible. If you are adopting a Chihuahua puppy into your family, let as many people handle him as possible as soon as you bring him home. If you have other dogs in your household, let them interact with your new Chihuahua. If this is a puppy, as always, be cautious with any older dogs or larger dogs around your new Chihuahua because he is small and tender. Under your close supervision, let your Chihuahua and your other pets explore and get to know one another. A social Chihuahua knows how to be friendly because he has been exposed to more than just his owner. A Chihuahua who lives and breathes for his owner only and does not know the breadth of the world around him can sometimes come off as aggressive or unfriendly. You can also teach an older Chihuahua to be friendly, it just may take more time for some of the older guys because they are set in their ways and need to learn new behaviors.
Start training your Chihuahua to be friendly as soon as you bring him home. To do this, be sure to socialize him as much as you can with people as well as with other pets. If you are introducing your Chihuahua to other pets, be sure to have treats for both animals on hand so they can meet on common ground over food. If you are introducing your Chihuahua to other animals that do not live in your home, be sure you know the owners and are comfortable with the animals to keep both animals safe during your initial meeting. Be persistent and consistent with his training. Your Chihuahua can be friendly to people and animals, but you have to insist he behaves as so. Keep your training sessions short with lots of rewards.