You have three things to consider:
- The possibility and expenses of roaming (using your home cell contract abroad).
- The possibility and inconveniences of using a local SIM in your home phone
- The costs of buying a new phone.
When you go abroad, the easiest, but the most expensive is to simply use your home phone there. This requires you to have roaming enabled on your contract. Contact your provider to ask and also make sure to ask about the costs. It can be VERY expensive.
The next easiest will be to buy a local foreign SIM card and use it in your existing phone. That requires your existing phone to be unlocked for this (also ask your phone provider or simply try someone else's phone card from a different provider). This has the advantage that you do not need to have another phone but the disadvantage that you will not be reachable on the home SIM since your phone won't ring in case someone calls your home phone number.
The most complicated way would be to get a new phone and get a foreign SIM card for it. The advantage is that you are always reachable. This would make sense if you have another unlocked old phone to use or if you can get one cheaply of eBay or such.