I have three older portable machines that are easy to tote. Featherweight - has no features but being super lightweight and cute. Brother 420 (before it became PRW) - all the features you will ever need. Janome Gem Gold - older model and it's a perfect basic machine.
I sometimes take my Bernina 1260 but it is heavy even though it is not that big in size. My favorite? I guess it would be the Brother.