Most Merfolk will Travel Using Crutches
There are a lot of answers here based on what merfolk of considerable wealth could choose from, but the idea of persons of normal means owning any sort of vehicles is a pretty new concept.
Instead, consider that merfolk are basically no different on land than a 1-legged human. The use of wooden crutches as a means for 1-legged people getting around goes back to atleast 2830 BC; so, it's not hard to imagine them being interjected into almost any setting. With conditioning, it is very much possible to travel over 10 miles in a day on them which means that a reasonably fit merperson could travel just as far on them as a commoner would ever realistically be expected to walk in a day.
Furthermore, crutches do not require you to transition between modes of travel. A Merperson, could come out of the water, travel the few miles it takes to get into town, and "walk" right into the building they were going to.
This answer applies to mermaids as described by the OP, not all versions of mermaids.
(they) have a life style similar to seals... they can scuffle across the ground similar to sea lions... (they have) fused thighs...
Len brings up a few good points in comments that would apply to a mermaid with a literal fish tail, but these mermaids by their description appear to be aquatic mammals and not fish at all.
When you look at the tails of aquatic mammals like seals, sea lions, dolphins, or whales, they bend in the dorsal/ventral direction like human legs, not in the side-to-side fashion of a fish tail. More ovever, since the OP describes the tail as fused leg bones, and not an extension of the spine, this further implies that the OP's mermaids are most likely a viable evolutionary branch of the sirenomelia mutation. Survivors of sirenomelia who have had their legs surgically separated are proven to be able to walk on their legs; so, to have a tail made of two legs fused together would likewise be able to support one's weight when standing. It can also be assumed that the "fin" at the back is much thicker and "foot like" than a fish's tail fin as you see on aquatic mammals or people with sirenomelia. Worst case scenario, your mermaid will need some kind of shoe to prevent abrasions while it walks, but human commoners already wair shoes all the time, so this is a pretty reasonable expectation in addition to the crutches
As for concerns about needing to stay wet, seals and sea lions can live indefinitely out of water. In captivity, injured seals are often kept out of water for months at a time as their injuries heal; so, if these merfolk have seal like lifestyles, this means any answer that mentions keeping the mermaid wet is unnecessary.
What about those scales?
While we generally expect to see merfolk with scaly tails, no one ever said those scales belong to the mermaid. They could wear fish leather tail coverings which would have a similar function to all-in-one pants and shoes while further perpetuating the "half-fish" misconception by showing off a scally lower half. In reality, their lower half could actually be more like a dolphin or seal tail.