Depends on how early you want to check in, where you want to stay, how much you want to pay, what time of year you are traveling. Just about any hotel will hold your bags if your room isn't ready when you arrive. I was just in Dublin last week and arrived around 2pm for a 4pm check-in, thinking we'd just leave our bags. The room was ready, so we were able to check in. This was a week day in March, so not high season, and not super early in the day. If you want to guarantee you can check in upon arrival, book the night before and let the hotel know of your plans.